refactoring: case(for power and modulus)

src/main/c/Calculator/calculator.c

@@ -80,6 +80,10 @@ double combination(int n, int r);
             return num1 * num2;
         case 4:
             return num1 / num2;
+        case 5:
+            return pow(num1, num2);
+        case 6:
+            return fmod(num1, num2);