U.S. T-Bill Refer to Fig. 1, where f(t) is the percentage yield (interest rate) on a 3-mon...

U.S. T-Bill Refer to Fig. 1, where f(t) is the percentage yield (interest rate) on a 3-month T-bill (U.S. Treasury bill) t years after January 1, 1980.

(a) What was the average rate of change in the yield from January 1, 1981, to January 1, 1985?

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(b) How fast was the percentage yield rising on January 1, 1989?

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(c) Was the percentage yield rising faster on January 1, 1980, or January 1, 1989?

Figure 1 Percentage yield on 3-month T-bill (1980–1992).