Sodium-24 is a radioactive isotope of sodium that is used to study circulatory dysfunction. Assuming that 4 micrograms of sodium- 24 is injected into a person, the amount A in micrograms remaining in that person after t hours is given by the equation A = 4e^-0.0046a. Graph this equation. b. What amount of sodium- 24 remains after 5 hours? c. What is the half-life of sodium-24? d. In how many hours will the amount of sodium- 24 be 1 microgram?