Delilah needs to design boxes with a volume of 21x^{2} +14x-35. The dimensions of the product within the boxes restrict the length of the boxes to 7 and the height of the boxes to x-1. What will be the width of the boxes?
a) 3x^{2}+2x-5
b) 2x+35
c) 2x-35
d) 3x-5
e) 3x+5