For each of the following constraints of pure BIP problems, identify which ones are made redundant by the binary constraints. Explain why each one is, or is not, redundant.
(a) 2x1 + x2 + 2x3 ≤ 5
(b) 3x1 – 4x2 + 5x3 ≤ 5
(c) x1 + x2 + x3 ≥ 2
(d) 3x1 – x2 – 2x3 ≥ –4