You are going to considering two cell phone providers i.e. UFONE and Telenor. UFONE charges Rs.599 (super card) per month for the service regardless of the number of phone calls made while Telenor does not have a fixed service fee but instead charges Rs. 2 per minute for calls. Your monthly demand for minutes of calling is given by the equation

Qd = 150 - 50P, where P is the price of a minute

a. With each service provider, what is the cost to your brother of an extra minute on the phone?

b. In light of your answer to (a) part, how many minutes would your brother talk on the phone with each service provider?

c. How much would he end up paying each provider every month?