added new solved vat calculation and calid phone number

Author: shihabuddin-dev

F. Function/special-problem/valid-phone-number.js

@@ -0,0 +1,13 @@
+function validContact(contact) {
+    if (contact.length === 11 && contact.startsWith("01") && !contact.includes(" ")) {
+        return true;
+    }
+    else if (typeof contact !== 'string') {
+        return "Invalid";
+    }
+    else {
+        return false;
+    }
+}
+const number = validContact(true);
+console.log(number);

F. Function/special-problem/vat-calc.js

@@ -0,0 +1,11 @@
+function calculateVAT(price) {
+    if (typeof price !== 'number' || price < 0) {
+        return "Invalid";
+    }
+    else {
+        const productVat = price * 7.5 / 100;
+        return productVat;
+    }
+}
+const result = calculateVAT(1000);
+console.log(result);