The weekly demand for comfort pillows is given by 400 p(x) = + 7, 000 where a is the number of pillows produced and sold, and p is in dollars. Using the Marginal Revenue function, R' (x), approximate the marginal revenue when 10 pillows are produced and sold. O $1,100 O $1,500 O $3,400 O $4,500 O $3,200