If 0 < a < b and a^2 + b^2 = 50, ab = 7, what is b − a?

1. Identify what is being asked: this is a **Algebra** question. 2. Apply the standard approach for this question type to evaluate each option. 3. The correct answer is **B. 4** — it satisfies the conditions of the stem. _Source: GMAC Official 12 Sample Questions (mba.com)_