I need help on my homework

For a certain automobile, M(x) = -0.015x" + 1.41x-7.2, 30sxs 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 integers or decimals rounded to the nearest thousandth as needed.) (A) The absolute maximum miles per gallon is This occurs at mph. (Type integers or decimals rounded to the nearest thousandth as needed.) (B) The absolute minimum miles per gallon is This occurs at mph. (Type integers or decimals rounded to the nearest thousandth as needed.)