Company a charges $0.32 dollars per minute (no fixed monthly charge). company b charges $13.9 per month plus $0.28 per minute. company c charges a fixed rate of $50 per month. let and () denote the monthly charges of company a, b, and c respectively for spending minutes on long distance calls. find a formula for the monthly cost of using company a, a(x): a(x)=  find a formula for the monthly cost of using company b, b( x ): b(x) =  find a formula for the monthly cost of using company c, c(x): c(x) =

For this case, the first thing we must do is define variables.

We have then:

x: number of minutes

A (x), B (x), C (x): total cost of companies A, B and C, respectively.

We must write a function of the form:

Where,

m: is the cost per minute

b: it is the fixed cost.

For the company A we have:

For company B we have:

For company C we have:

The cost of each company monthly is:

For this case, the first thing we must do is define variables.

We have then:

x: number of minutes

A (x), B (x), C (x): total cost of companies A, B and C, respectively.

We must write a function of the form:

Where,

m: is the cost per minute

b: it is the fixed cost.

For the company A we have:

For company B we have:

For company C we have:

The cost of each company monthly is: