To change the Calculate () function to return the product instead of the sum, how many lines of code need to be changed? int Calculate (int a, int b) { return a + b; int main(void) { printf("%d", Calculate (3, 4)); printf("%d", Calculate (5, 2)); printf("%d", Calculate (6, 7)); return 0; O a. 1 O b.2 O c. 3 O d. 4