17 how many integer solutions are there to the equation x 1 + x 2 + x 3 + x 4 = 132 x1+x2+x3+x4=132 provided that x 1 > 0 , x1> 0, and x 2 , x 3 , x 4 ≥ 0 ? x2,x3,x4≥0? what if we add the restriction that x 4 < 17 ?