problem on finding max value (URGENT)

I was wondering what would be the way to answer this question. I know that trial error is one way but i also know that there is a differential calculus like method. But i am not sure about how to do it. Could some one pleaes help me!!!!!

"Find the length of the cuboid which has a maximum permissible length of 1.070m and also has the maximum possible volume"

**NOTE**: must ensure that sum of the maximum length and the corresponding circumference (circumference of plane perpendicular to length)

All help is appreciated.