i need 17 and 22 please

For Exercises 16 - 18, find the x-value(s) where the graph of the function has a horizontal tangent line. 16. f(x) = 4x' - 14.x2 + 8x - 13 17. f(x) = 5x4 + 20x3 - 6 7 18. f(x) = {x7x+29 ) 19. Suppose that the profit, in dollars, obtained from the sale of x barbeque dinners is given by P(x) = -0.03x2 + 8x - 50. Find the rate of change of profit when 40 barbeque dinners are sold. 20. The cost of producing x calculators per week is given by C(x) = 600 + 100 Vx dollars. Find the marginal cost when 250 calculators are produced each week. 21. A flat iron manufacturer has a revenue function, in dollars, given by R(x) = 35x -0.12%, where x is the number of flat irons sold. (a) Find the marginal revenue when 160 flat irons are sold. 1 (b) Find the rate of change of revenue when 200 flat irons are sold. 22. An arrow shot upward from the ground will have a height of s(t) = - 1612 + 128 feet after 1 seconds. Find the velocity of the arrow after 3 seconds