The number of farms in the United States t years after 1925 is f(t) million, where f is the function graphed in Fig. 26(a). [The graphs of f'(t) and f"(t) are shown in Fig. 26(b).] 6 5 4 3 2 1 y 0 (1925) 10 20 y=f(t) t 40 30 40 50 60 70 (a) 20 30 0 -.05 -.1 Y Figure 26 10 20 30 40 50 60 70 y=f"(t) y = f'(t) (b) (a) Approximately how many farms were there in 1990? (b) At what rate was the number of farms declining in 1990? (c) In what year were there about 6 million farms? (d) When was the number of farms declining at the rate of 60,000 farms per year? (e) When was the number of farms declining fastest?