How to change an answer to an equation based on tickbox

I'm new to coding even more so on excel or google sheet. I'm currently trying to make a simple Combination and Permutation calculator based on a true or false statement in a tickbox, if true then it will calculate the combination of n and r. If false then it will calculate the permutation of n and r.

Here's a little demonstration of what I'm trying to achieve:

So, I would like to make an "if statement" that checks the true or false statement in C5, then if it's true, simply do "=COMBIN(B3, D3)" and if it's false, then do "=PERMUT(B3, D3)". Then print the result to C10.