Calculus
posted by Destinee .
At the moment OHaganBooks is selling 1000 books per week and its sales are rising at a rate of 200 books per week. Also, it is now selling all its books for $20 each, but the price is dropping at a rate of $1 per week. I need to know at what rate OHaganBooks' revenue is rising or falling given these conditions. I would also like to see the company's revenue increase at a rate of $5000 per week. At what rate would sales have to have been increasing to accomplish this?
Can somebody help me answer this and explain the steps to solve the problem?

write the functions.
revenue= number books sold * price book
dRev/dt=n dp/dt + p dn/dt
you are given n, p and dp/dt, and dn/dt
calculate.
For the second part, set dRev/dt to 5000
find dn/dt given n, p, dp/dt
I will be happy to critique your work. 
ok i got this
R=(1000+200x)(20x)
R'=3000400x
is that right so far? 
and x=weeks?