7. Please show your work. Thank you

For a certain automobile, M(x) = - .015x" + 1.43x - 7.9, 30 5xs 60, represents the miles per gallon obtained at a speed of x miles per hour. (a) Find the absolute maximum miles per gallon and the speed at which it occurs. (b) Find the absolute minimum miles per gallon and the speed at which it occurs. (a) The absolute maximum miles per gallon is . This occurs at mph. (Type an integer or decimal rounded to the nearest thousandth as needed.)