The following code contains two classes both containing implementations of the factorial function. Calculator works fine for positive numbers, but not for negative numbers or 0. SafeCalculator tries to solve this problem by throwing an exception when negative or 0 input values are encountered. Note that both classes can be compiled successfully. public class Calculator ( public int factorial (int input) { if (input--1) return 1; else return input factorial (input-1); } public class SafeCalculator extends Calculator | @Override public int factorial (int input) { if (input 1,2->2,3-6,4->24) are correctly calculated by Calculator. [2 marks] (d) Assume you have written all test cases in question c) correctly, and all those tests pass. Does this imply that Calculator is a correct implementation of the factorial number algorithm? Discuss! [2 marks]