diff --git a/2_Scope_Closures/practice_new/closure_part3_nkang.js b/2_Scope_Closures/practice_new/closure_part3_nkang.js
new file mode 100644
index 0000000..f9aa7ec
--- /dev/null
+++ b/2_Scope_Closures/practice_new/closure_part3_nkang.js
@@ -0,0 +1,100 @@
+function calculator() {
+	let strNum = "";
+	let leftNum = 0;
+	let rightNum = 0;
+	let oprt = "";
+
+	return function pressKey(key) {
+		if (/\d/.test(key)) {
+			strNum += key;
+			return key;
+		}
+		else if (/[+*/-]/.test(key) && oprt == "") {
+			leftNum = strNum ? Number(strNum) : leftNum;
+			strNum = "";
+			oprt = key;
+			return key;
+		}
+		else if (/[+*/-]/.test(key) && oprt != "") {
+			leftNum = fourRules(leftNum, oprt, Number(strNum));
+			strNum = "";
+			oprt = key;
+			return key;
+		}
+		else if (key == "=") {
+			leftNum = fourRules(leftNum, oprt, Number(strNum));
+			strNum = "";
+			oprt = "";
+			return leftNum;
+		}
+	}
+}
+
+function fourRules(num1, oprt, num2) {
+	if (oprt == "+") return num1 + num2;
+	else if (oprt == "-") return num1 - num2;
+	else if (oprt == "*") return num1 * num2;
+	else if (oprt == "/") return num1 / num2;
+	else return "err";
+}
+
+var calc = calculator();
+
+function useCalc(calc,keys) {
+    return [...keys].reduce(
+        function showDisplay(display,key){
+            var ret = String( calc(key) );
+            return (
+                display +
+                (
+                  (ret != "" && key == "=") ?
+                      "=" :
+                      ""
+                ) +
+                ret
+            );
+        },
+        ""
+    );
+}
+
+function formatTotal(display) {
+    if (Number.isFinite(display)) {
+        // constrain display to max 11 chars
+        let maxDigits = 11;
+        // reserve space for "e+" notation?
+        if (Math.abs(display) > 99999999999) {
+            maxDigits -= 6;
+        }
+        // reserve space for "-"?
+        if (display < 0) {
+            maxDigits--;
+        }
+
+        // whole number?
+        if (Number.isInteger(display)) {
+            display = display
+                .toPrecision(maxDigits)
+                .replace(/\.0+$/,"");
+        }
+        // decimal
+        else {
+            // reserve space for "."
+            maxDigits--;
+            // reserve space for leading "0"?
+            if (
+                Math.abs(display) >= 0 &&
+                Math.abs(display) < 1
+            ) {
+                maxDigits--;
+            }
+            display = display
+                .toPrecision(maxDigits)
+                .replace(/0+$/,"");
+        }
+    }
+    else {
+        display = "ERR";
+    }
+    return display;
+}
\ No newline at end of file
diff --git a/2_Scope_Closures/practice_new/closure_part4_nkang.js b/2_Scope_Closures/practice_new/closure_part4_nkang.js
new file mode 100644
index 0000000..4d539b4
--- /dev/null
+++ b/2_Scope_Closures/practice_new/closure_part4_nkang.js
@@ -0,0 +1,122 @@
+function calculator() {
+  let strNum = "";
+  let leftNum = 0;
+  let oprt = "";
+
+  let publicAPI = {
+    number,
+    eq,
+    plus() { return operator("+"); },
+    minus() { return operator("-"); },
+    mult() { return operator("*"); },
+    div() { return operator("/"); }
+  };
+
+  return publicAPI;
+
+  function number(key) {
+    if (/\d/.test(key)) {
+        strNum += key;
+        return key;
+      } 
+  }
+
+  function eq(key) {
+    if (key == "=") {
+        leftNum = fourRules(leftNum, oprt, Number(strNum));
+        strNum = "";
+        oprt = "";
+        return leftNum;
+      }
+  }
+
+  function operator(key) {
+    if (oprt == "") {
+        leftNum = strNum ? Number(strNum) : leftNum;
+    }
+    else if (oprt != "") {
+        leftNum = fourRules(leftNum, oprt, Number(strNum));
+    }
+    strNum = "";
+    oprt = key;
+    return key;
+  }
+
+  function fourRules(num1, oprt, num2) {
+    if (oprt == "+") return num1 + num2;
+    else if (oprt == "-") return num1 - num2;
+    else if (oprt == "*") return num1 * num2;
+    else if (oprt == "/") return num1 / num2;
+    else return "err";
+  }
+}
+
+var calc = calculator();
+
+function useCalc(calc, keys) {
+  var keyMappings = {
+    "+": "plus",
+    "-": "minus",
+    "*": "mult",
+    "/": "div",
+    "=": "eq"
+  };
+
+  return [...keys].reduce(
+    function showDisplay(display, key) {
+      var fn = keyMappings[key] || "number";
+      var ret = String(calc[fn](key));
+      return (
+        display +
+        (
+          (ret != "" && key == "=") ?
+            "=" :
+            ""
+        ) +
+        ret
+      );
+    },
+    ""
+  );
+}
+
+function formatTotal(display) {
+  if (Number.isFinite(display)) {
+    // constrain display to max 11 chars
+    let maxDigits = 11;
+    // reserve space for "e+" notation?
+    if (Math.abs(display) > 99999999999) {
+      maxDigits -= 6;
+    }
+    // reserve space for "-"?
+    if (display < 0) {
+      maxDigits--;
+    }
+
+    // whole number?
+    if (Number.isInteger(display)) {
+      display = display
+        .toPrecision(maxDigits)
+        .replace(/\.0+$/, "");
+    }
+    // decimal
+    else {
+      // reserve space for "."
+      maxDigits--;
+      // reserve space for leading "0"?
+      if (
+        Math.abs(display) >= 0 &&
+        Math.abs(display) < 1
+      ) {
+        maxDigits--;
+      }
+      display = display
+        .toPrecision(maxDigits)
+        .replace(/0+$/, "");
+    }
+  }
+  else {
+    display = "ERR";
+  }
+  return display;
+}