Fix error in addition implementation

compute.js

@@ -11,7 +11,7 @@ function Compute() {
      */
     // TODO: modify with the correct operator
     // We intentionally kept this mistake: * operator instead of + operator
-    this.add = (a, b) => Number(a) * Number(b);
+    this.add = (a, b) => Number(a) + Number(b);
     /**
      * @method sub
      * @desc Calculate the difference between two numbers