Tasks P, Q, R, S must be completed in some order. P must be before R. Q must be before S. R must be before S. Which is a valid order?

✓ Correct Answer: Option B

Constraints: P < R, Q < S, R < S. So P < R < S and Q < S. B: P(1) < R(3) ✓, Q(2) < S(4) ✓, R(3) < S(4) ✓. Valid.