If statement to sum if cell contains certain txt

I am trying to get an if statement to sum based on certain criteria. I have attached a screen shot for better understanding. Essentially what I want to achieve is this. In my screen shot Cell U4 is the sum of Cell R4:T4 This is fine but what I want to incorporate is that if Cell O4 contains "yes" then sum and show the number which is fine but if Cell O4 contains "No" then show me the text "fail"

Screen shot below, and as always thank you so much for any help you can give