A record club has found that the marginal profit, P'(x), in cents, is given by P'(x) = -0.0005x3 + 0.38x2 + 61.5x for x 700, where x is the number of members currently enrolled in the club. Approximate the total profit when 420 members are enrolled by computing the sum 6 P' (xi) Ax with Ax = 70. i=1 The total profit when 420 members are enrolled is approximately $. Round to the nearest cent as needed.) AP'(x)=-0.0005x3 +0.38x+61.5x O 66,000 52,800- 39,600 G 26,400- Marginal profit (in cents) 13,200- 0- 0 VV V 100 200 300 400 500 600 700 Number of members.