Waterway reported the following results from the sale of 5000 units in May: sales $310000, variable costs $190000, fixed costs $90000, and net income $30000. Assume that Waterway increases the selling price by 5% on June 1. How many units will have to be sold in June to maintain the same level of net income? a) 4428. b) 4605. c) 5000. d) 4750.