Your aunt matilda passes away and leaves you with the tidy sum of $50,000. you find a bank that will pay you 5.15 % per year compounded every instant. you want to enjoy some of this money, but you don't want to blow it away too fast. you decide to deposit the $50,000 but to pull out d dollars per year so that after t years, you will have blown (d t) dollars off. if p [t] is the amount in the account, then why does p [t] solve the differential equation p'[t] - 0.0515 p[t] = -d ?