A trainee saves £2,400 and expects to spend £180 each week while retraining. Which rule gives the money left, M, after w weeks?

1. The money left starts at £2,400 before any weeks have passed, so 2400 is the starting value. 2. Each week takes £180 away, so the rate of change is minus 180 pounds per week. 3. Putting those together gives money left equals 2400 minus 180 times the number of weeks. 4. Option A adds the spending instead of taking it away, which would make the savings grow. 5. So the rule is M = 2400 - 180w, option B. _Source: OpenStax College Algebra (CC BY 4.0), Ch 4 "Linear Functions", section 4.2 Modeling with Linear Functions_