U. 6.8 Write function headers (not the bodies) for the following functions: a. Return a sales commission, given the sales amount and the commission rate. b. Display the calendar for a month, given the month and year. c. Return a square root of a number. d. Test whether a number is even, and return true if it is. e. Display a message a specified number of times. UDON f. Return the monthly payment, given the loan amount, number of years, and annual interest rate. g. Return the corresponding uppercase letter, given a lowercase letter immediate int) fun