Problem 5. (1 point) Consider the function f(a) = a7 - 7ac. For what values of a do we have that both f(a) is decreasing and the graph of y = f(a) is convace up? Write your answer as a list of intevals. For example, if the f(a) were decreasing and concave up on (-29, -3) U (17, 100), write (-29,-3), (17,100). Answer =