Answers
Let usage of indifference = P minutes
Case 1: Regular Plan
Fixed fee = $55 per month
No variable cost till 1000 minutes and $0.33 per minute after 1000 minutes
Total cost = 55 + [(P - 1000) x 0.33] (Provided P > 1000)
Case 2: Executive Plan
Fixed fee = $100 per month
No variable cost till 1200 minutes and $0.25 per minute after 1200 minutes
Total cost = 100 + [(P - 1200) x 0.25] (Provided P > 1200)
For the point of indifference,
Total cost (Regular Plan) = Total cost (Executive plan)
55 + [(P - 1000) x 0.33] = 100 + [(P - 1200) x 0.25]
55 + 0.33P - 330 = 100 + 0.25P - 300
0.33P - 0.25P = 100+330-55-300
0.08P = 125
P = 1562.5 Minutes
At the usage of 1562.5 minutes per month, both the plans will have the same utility and fee.
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