4. [4 marks] In the program below, assume that n1 and n is a perfect square: that is, there is zZ such that n=z2. Find a function f(n) that counts the number of times that expensiveFnc() is called, as a function of the input size n. Make sure that you are only counting calls to expensiveFnc() and not any other steps. You can use the given loop invariant without proof. 1234567891011//pre:nasdescribeda0k1//LoopInv:(aZ)(k==(a+1)(a+1))while(k<>