A company has found that its weekly profit from the sale of x units of an auto part is given by P(x) = -0.02x³ + 600x - 20,000. Production bottlenecks limit the number of units that can be made per week to no more than 150, while a long-term contract requires that at least 50 units be made each week. Find the number of units that must be sold each week to maximize profit. Find the maximum weekly profit.