5 5p 10x 300 0 is the demand function What is the marginal

5. 5p + 10x+ 300 - 0 is the demand function. What is the marginal revenue at x - 202 a) -$140 b) $2000 c) -$1280 d) None of the above -S The Side of a square is decreasing at a rate of 2 cm/second. At what rate is the Area decreasing when the side is 8cm? 6.

Solution

5)    5p + 10x + 300 = 0 =====> p = -2x – 60

     Then total revenue = TR = p*x = -2x^2 – 60x

     Then marginal revenue = MR = d(TR)/dx = -4x – 60

    At x = 20,   MR = -4*20 – 60 = -80 – 60 = -$140    (option A)

6) Let side = L = 8 cm

     dL/dt = -2 cm/s

     Area = A = L^2

     Then dA/dt = 2L*dL/dt = 2*8*(-2) = 32 cm^2/s