Q8 (8 points) C(y) = 21y3 - 7y2 + - y + 83, y 2 0 is a firm's cost function. Find the interval over which this function is strictly concave and the interval over which it is strictly convex. Write your answer in interval notation such as [a, b], work with fractions rather than decimals. + Drag and drop an image or PDF file or click to browse