Since 1990, the purchasing power of a country's dollar, a) P(10) = as measured by consumer prices, can be modeled by the function below, where x is the number of years since (Round to two decimal places as needed.) 1990 P(X) = 1 + 0.0395x 0.8- 0.6- Purchasing power (dollars) 0.4- 0.2- P(X) = 1 + 0.0395x vX 5 10 15 20 25 30 Years since 1990 ef a) Find P(10), P(20) and P(40). b) When will the purchasing power be $0.80? c) Find lim P(x). X + 00