Suppose that on the interval , is positive and concave up. Furthermore, assume that exists and let . Use this information to answer the following questions.

To answer the questions, choose your answers from the following list:

CU (concave up), CD (concave down), f(x) , f'(x) , f''(x) , 0 , or 1 .

a.) on .

b.) , where and .

c.) on .

d.) is on .

You can earn partial credit on this problem.