can't write proper if statement

I can't seem to get the formula right.

It is a salesperson bonus

I have the over margin dollars in J7. (this could be a negitave number)

I wanted to write a formula using J7 number.

IF J7 is less than 0 = 0
IF J7 is greater than 0 but less than 50,000 they get 7.5% commission of J7
IF J7 is greater than 50,000 they get 7.5 % of the first 50,000 and 5% of the amount over 50,000

Thanks for any help