Find the area under the graph of f over the interval [2,9]. 8x +7, for x$6 f ( x ) = 3 73 7X, for x > 6 The area is . (Type an integer or a simplified fraction.)A clothing company determines that its marginal cost, in dollars per dress, is given by the function below. Find the total cost of producing the rst 210 dresses, disregarding any fixed costs. 3 C'(x) = - EX + 48, for x s 450 The total cost is $ . (Round to the nearest cent as needed.) Find k such that the function is a probability density function over the given interval. Then write the probability density function. f(x) = kx2, [ 2,5] k= (Type an exact answer.) The probability density function is f(x) = . (Type an exact answer.)