Since you are given the area of the base=252 can solve for the length and width. let w = width then length is (w+4) so w(w+4)=252 w^2 +4w -252 = 0 now factor and solve
(w+18)(w-14) =0
w=14 discard the solution w=-18 since you can have a negative length
So width = 14
length = w+4 =18
height = w-2 = 12
Volume = l x w x h
Volume = (14)(18)(12)= 3042 sq inches