Question: Consider the proposition 2x + 5 ≥ 13.
(a) Is the condition x ≥ 0 necessary, or sufficient, or both necessary and sufficient for the inequality to be satisfied?
(b) Answer the same question when x ≥ 0 is replaced by x ≥ 50.
(c) Answer the same question when x ≥ 0 is replaced by x ≥ 4.