Three celluar telephone companies have different fee plans for local calls.

i. talk-it-up offers a flat rate of $50 per month. you can talk for as much as you would like for no extra charge.
ii. one thin dime charges $0.10 for each half minute with no flat fee.
iii. cellbell charges $30 per month and then $0.10 per minute for all calls made.

a. for each company, write an equation that relates the cost of the phone service c to the number of minutes a customer talks during a month t.

b. any linear equation can be written in the form y = mx + b. give the value of m and b for each equation that you wrote in part a.

c. for each company, make a graph that relates the cost of the phone service to the number of minutes a customer talks during a month.

d. where do the values of m and b appear in the graph for each phone company?