Directional Derivative & Triple integral problems

Hi to all again =) I have 2 questions about directioanl derivate & Triple integral things.

**1)** The temparature in a rectangular box is approximated by

If a mosquito is located at , in which direction should it fly to cool off as rapidly as possible?

**2** A wedge is cut from a right circular cylinder of radius *R* by a plane perpendicular to the x-axis of the cylinder and a second plane that meets the first on the axis at an angle of degrees. Set up an evaluate a triple integral for the volume of the wedge.

These two are questions and i don't know where to begin so i couldn't make any progress.

Gonna be very appriciated for any help.