A firm is able to borrow up to ${b} million from its line of credit at any time. The interest rate is 0.5% per month and the company is required to maintain a compensating balance of 4% on any funds actually borrowed which will be deposited in a non-interest bearing account. Suppose the company needs $10,000,000 today and plans to repay it in six months. How much interest it needs to pay? 4% of compensating balance on any funds actually borrowed is still required.