I'm horrible at word problems but

Create a chart that has the following information for each of the three selected carriers: cost per month, base number of minutes, additional cost per minute (overage)

Using the information from the chart you created, write the total monthly cost, C, in terms of m minutes for each of the three carriers (3 points)

Select two of the three identified plans and calculate how many minutes it will take for the cost of the two plans to be the same. Show all work.

Now compare all three plans and determine if one plan is a better deal than the other two. Support your answer mathematically.

Which plan would you choose and why? Support your answer mathematically

My plans are:
ATT: $12 a month for 250 minutes at .05 for every over.
T Mobile: $3 a month for 30 minutes at .10 for every over
Virgin Mobile: $20 a month for 400 minutes at .10 for every over.

ATT: c(m) =

12.00 for m <= 250
12.00 + .05(m-250) for m>250

T Mobile: c(m) =
3.00 for m <= 30
3.00 + .10(m-30) for m > 30

Virgin: c(m) =
20.00 for m <= 400
20.00 + .10(m-400) for m>400

Now just figure the cost for various amounts of minutes, especially where the price breaks occur.