Question 2 • Applications and Modeling
Each increase of 20 minutes raises the monthly cost by $2.40: $25.35 − $22.95 = $2.40, $27.75 − $25.35 = $2.40, and $30.15 − $27.75 = $2.40. The rate of change is therefore constant at $2.40 ÷ 20 = $0.12 per minute, matching the contract. The data represent a linear function, so the correct choice is “Yes, the average rate of change is constant.”
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