The Following Table Shows the Numbers of U

The following table shows the numbers of U.S. cellular subscriberships (in millions) from 1985 to 2002. ​ Source: The CTIA Semi-Annual Wireless Industry Survey
Assume that the number of U.S. cellular subscriberships, in millions, can be modeled by the function , where t is the number of years past 1980. Use the second derivative to estimate how fast the rate of increase in subscriberships was changing in 1991 in millions of subscriberships per year.
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A) 121.08
B) -121.08
C) 1.08
D) -1.08
E) 0