Consider the function f(x) = x - 5 x2 - 9 Determine the number of points on the graph of y = f(x) that have a horizontal tangent line. In other words, determine the number of solutions to f'(x) = 0. Determine the values of x at which f(x) has a horizontal tangent line. Enter your answer as a comma-separated list of values. The order of the values does not matter. Enter DNE if f(x) does not have any horizontal tangent lines. /1 Points] DETAILS MY NOTES The sales of a math performance enhancing drug are given by S(t) = 210t + 1 12 + 7 where t is in years and S(t) is in millions of dollars. What is the rate of change of sales in millions of dollars per year when t = 0? s'(0) = millions of dollars per year