calculus in true and false statements

1) State whether the following are true or false, and explain your answer: a. If f (x) and g(x) are both concave up at x = a, then h(x) = f(x) + g(x) could be either concave up or concave down at x = a. b. A cubic polynomial function could have two inflection points. c. If f'(c) is undefined, then f(c) must be undefined as well