Mike wants to open his own repair shop, and is considering using his savings of $30,000 to get it started. He is currently earning 3 percent interest on his savings. His friend Bob calls him and asks to borrow $30,000 to start up a bagel shop; Bob offers to pay him 5 percent interest if he loans him the money. If Mike were to use the money to open his own repair shop, how can he accurately account for his costs?