(in c prog.) what is the difference between scanf, getche and getchar?

Assignment: permutations use the permutation formula   r ! ! n n p nr   to solve each problem. be sure to show all work leading to your answer. part i: solve real-world permutation problems choose any four (4) of the following five problems to solve. for each problem a) show how the permutation formula can be used to find the answer and b) write a sentence to explain the meaning of the answer for the situation. 1. to register for online banking services at a local credit union, you need to select a four-digit personal identification number, or pin code. the digits cannot be repeated. how many ways are there to arrange four digits out of the numerals 0 through 9 to create a code?