4. The number of farms, in thousands, with milk cows may be modeled by C(t) =191.51(0.94)' , where t is the number of years since 1990. (Source : Statistical Abstract of the United States, 2007, Table 846) a. How many farms had milk cows in 1990? b. By what percent is the number of farms changing? c. Using logarithms determine the year when will there be 10 thousand farms with milk cows. d. Using mathematics, explain if there will ever be zero farms with milk cows