$1.$ Write a C$++$ program that does the following: a$.$ Create a C$++$ file with the name problem$1.$cpp$.$ b$.$ Implement the following four functions used in the main function given below. c$.$ int numberOdd$($int x$,$ int y$)$ returns how many of its two arguments are odd. d$.$ int closest$($double x$)$ returns the closest integer to argument x$.$ e$.$ int max$($int a$,$ int b$,$ int c$,$ int d$)$ returns the maximum of the four arguments. f$.$ int firstDigit$($int x$)$ returns the leftmost digit of the argument. Assume the argument is positive. g$.$ Type in the following main function into your C$++$ program file: