An upstart phone company has only two potential large customers, Firm A and Firm B. Firm A's monthly demand for phone calls are Q1 =2,800 -200p (with p measured in cents) and Firm 2's is Q2 = 5,000 -100p. The marginal cost of providing a phone call is 6 cents. Assuming the phone company has to charge the same monthly rental fee and unit price to all its customers, at what level should it set these charges?