Google Sheets multiple conditions with nested If statements?

I'm really struggling with this formula, but I think I'm overthinking it. I'm not sure what's the proper way to write this:

What I want to happen is: If cell A1 = John AND cell B1 = Buyer then take the dollar amount in C1 and multiply it by 10% ELSE If cell A1 = John AND cell B1 = Seller then take the amount in C1 and multiple it by 25% BUT If A1 is NOT equal to John, then return a currency value of $0

I sincerely appreciate any help. Thank you! Lisa