For the problem below, a. Write a function that describes exponential decay. b. Use your calculator to graph the function. c. Evaluate the function at the given values. Round answers to one decimal place. Plutonium-238 is a radioactive element that decays over time into a less harmful element at a rate of 0.8% per year. A power plant has 50 pounds of plutonium-238 to dispose of. How much plutonium- 238 will be left after 10 years? After 100 years? a. N(t) = c. 10 years: 100 years: lb Ib