Let f (t) be the number of ducks in a lake 1' years after 1990. a. What does the statement f(7) = 31 mean? 0 In 1997, there were 31 ducks in the lake. 0 In 1997, there were 31 more ducks than in 1990. 0 There will be 31 ducks in the lake 7 years from now. 0 In 31 years, there will be 7 ducks in the lake. b. What does the statement f(19) = 38 mean? 0 In 38 years, there will be 19 ducks in the lake. 0 In the year 2009, there were 38 ducks in the lake. 0 There will be 38 ducks in the lake 19 years from now. 0 Every 19 years, there are 38 more ducks in the lake