Can you please provide an explanation to the answer of this question?

3. Jasmine lives where cell phone coverage is poor, so Jeremy can either call her on the landline phone for five cents per minute or he can drive to see her, at a round-trip cost of $2 in gasoline money. He has a total of 510 per week to spend on staying in touch. Calculate Marginal utility and Marginal utility per dollar spent and determine the utility maximizing combination of round trips and phone minutes. Round Total Marginal MU/ P Phone Total Marginal Utility MU I P Trips Utility Utility Minutes Utility Per minute 0 0 0 Cl 0 U 0 U 1 80 80 SCI/$2 = 40 40 380 380MB = 9.5 95,3535 = 190 2 150 TU TUE-$2 = 35 80 680 300MB = 7.5 17.51-75.05: 150 3 210 60 60/32 =30 120 900 2203340 = 5.5 iii/$.05: 110 4 260 50 50,912 = 25 160 1040 140/40 =35 15,338.05 = 70 5 300 40 40,332 = 20 200 1100 60f40 = 1.5 15/395 = 3|] Utility maximizing point is at 3 round trips and 200 phone minutes