Physic problems. Anyone know? I need your guide to do it.

Currently my sister is working on her physics exercise problems and she asked me how to do it.
I learn these before but forget the formulas since graduated.


The question sounds like this:

In free space the potential due to an E field is described by
V=(x^2)(y)(z+3) Volts.

Find:
(1) "the value of the E field at P(3,4,-6)" and
(2) "the charge within the cube described by 0<x,y,z<1"


I feel very thankful if any engineers or expertises people in this forum could help me out. Thanks a lot.