A closed rectangular box with faces parallel to the coordinate planes has one bottom corner at the origin and the opposite top corner in the first octant on the plane 3x + 2y + z = 1. What is the maximum volume of such a box?

Okay, on this one I do not know how to come up with my equation to then take the partial derivatives of and set them equal to zero, etc!!! I know from looking up first octant that it will be the first value with all three positive coordinates but I need MUCH help!!!! Thanks for taking your time to read this. Frostking