9. (a) Determine exact values for a and b so that the exponential function g(1) = ab' passes through the points (7,9) and (12, 11). Show all of your work and thinking fully. (b) By selecting constants a, b, and c, give an example* of a function of the form f(t) = c + ab' that has the following properties: f is always decreasing, f is always concave up, and as t - co, f(1) - 17.24. Write at least one sentence to explain how you chose your values of a, b, and c, and why you picked "+" or "-". Clearly justify why your choices result in the function's value approaching 17.24 as t - co. (* there are many, many examples that work; you just need to think about the characteristics of f and what you need to be true of a, b, and c.)