the price p and the quantity x sold of a certain product obey the demand equation

Question

p=(-1/3)x + 100

o is < or equal to x < or equal to 300

A) express revenue R as a function of x

b) what quantity x maximizes revenue.

Answer 1

Revenue=p*x
you finish..

Take the deriviative of R with respect to x, set to zero, solve for x.

Answer 2

so would the revenue be

(-1/3)x + 100 * 300

I don't understand- how would you multiply by x is its inequalities?

Also, what is the deriviative?