write c++ code please Fadi has a safe with a lock that has 20 buttons that can each be clicked only once. Fadi remembers that the safe opens after clicking on 5 buttons but can't remember which 5 buttons. He decided to try every possible 5 buttons and wants to know how many trials he has to make Fadi knows from high school that this requires computing combinations (2C, or 20 choose 5). So he wrote a program to compute n choose k for any 1