6\" National health expenditures (in billions of dollars) from 1980 to 1996 are given by the function f(t) , in the graph to the left. {Q} (a) How much money was being spent at the beginning of 1981? '3\" $ 500 billion (b)Approximately how fast was the rate of spending increasing in 1990? $ 200 billion per year (c) One trillion dollars was being spent at the beginning of which year? 1988 (d) When was the rate of spending increasing at a rate of $300 billion per year? El 0 2 4 6 8 101214 Years after 1980 The blue curve shows national health expenditures in billions of dollars. The red curve shows its derivative.