F# Code help needed

C) Now it is time to declare some functions.

1. Dene the function add10, which takes an integer argument, adds 10 to it, and returns the result.

2. Dene the function add20, which uses add10 to add 20 to a given integer. (add20 is not allowed to use +".)

3. Dene the function add_mn that takes two integers m, n as arguments and returns m + 10 * n. For instance, add_mn 3 5 = 3 + 10*5 = 53. You are, however, not allowed to use addition and multiplication directly: instead, you must write a recursive solution that calls add10! (So add_mn 3 5 should be computed as 3 + 10 + 10 + 10 + 10 + 10.)