A person is given an injection of 800 milligrams of penicillin at time t=0. Let f(t) be the amount (in milligrams) of penicillin present in the person's bloodstream t hours after the injection. Then, the amount of penicillin because exponentially, and a typical formula is f(t)=800e^-0.3t. Complete parts (a) through (c) below. (a) give the differential equation satisfied by f(t). f'(t)=​