The amount (A) in milligrams of aspirin in a person's bloodstream can be modeled by A = (391t^2 + 0.112)/(0.218t^4 + 0.991t^2 + 1) where t is the time in hours after one dose is taken.

a. A second dose is taken one hour after the first dose. Write an equation to model the amount of second dose in the bloodstream.

b. Write a model for the total amount of aspirin in the bloodstream after the second dose is taken. (The second dose plus the first one)