Can someone please help me out with this... I know it's an easy problem for most of you but i'm having a lot of difficulty.

I need to get the derivative of s (t) = t^5/2 (7-t), t>= 0

The point i get up to and get stuck at is when trying to do the whole product rule thing. I get up to here and have no idea what to do:

s (t) = 6/2t^(3/2) (t-7) + (t^(5/2)) (1)

I'm not sure what to do after that.