The ordering and transportation cost C of components used in a manufacturing process is approximated by

where is measured in thousands of dollars and x is the order of the size in hundreds.

(a) Verify that . --done this--

(b) According to Rolle's Theorum, the rate of change of cost must be 0 for some order size in the interval (3,6). Find that order size.

I started b, and trying to find the derivative of the original equation got very hairy very quickly. Any help? Thanks so much in advance.