In the first interview, I asked to return all the subsets of a given set. The follow-up question was to write a function that gets a set and an index and returns a unique subset. In the second, I got a function r5() that returns a random number between 1 to 5 in a uniform probability, and with that function, I need to build r7() that returns a random number between 1 to 7 in a uniform probability.