Problem: In a certain region of space, the electric field is constant in direction (say horizontal, in the x direction), but its magnitude decreases from E = 500 N/C at x = 0 to E = 430 N/C at x = 25 m.
Part A: Determine the charge within a cubical box of side scripted l = 25 m, where the box is oriented so that four of its sides are parallel to the field lines.
Please help for the above problem, completely confused!! Show each steps if possible, Thanks.