How do I figure out the total revenue and marginal revenue. Do I just multiply 20+q/200 by q getting 20q+q^2/200? If so, the partial derivative is 20+q/100? Equating that to 20+q/200 gets q=0. What's going on?

Can someone help with parts E & F?  I got 100 for part C and 22 for part D?  Am I on target?

Regards,

Greg