Refer to the information in number 1 above to answer this question and exercise #6 below. Write an equation expressing your monthly cost using the below independent and dependent variables. Let x = additional minutes used. Let d = number of directory assistance calls made. Let r = number of long distance minutes used. Let u = USF monthly charge. Let y = total monthly bill You have to multiply each of the variables by the cost per unit (month, minute, call) and add them together.

Given that the monthly cell phone bill is determined by a fixed monthly fee of $35 for 300 anytime minutes and $.40 for each additional minute used.

Dependent variables can be the result of more than one independent variable.

Consider your phone bill as presented above. Aside from being charged for minutes over 300, you are charged $1.25 for each directory assistance call and $.75 per minute for long distance roaming calls. You also have to contribute at least $1.50 to the federally required Universal Service Fund per month and this value may vary on your phone bill but is not an independent variable.

To write an equation expressing your monthly cost using the below independent and dependent variables.

Let x = additional minutes used, then the cost for additional minutes used is given by 0.4x.

Let d = number of directory assistance calls made, then the cost for directory assisitance is given by 1.25d.

Let r = number of long distance minutes used, then the cost for long distance minutes is given by 0.75r.

Let u = USF monthly charge.

Let y = total monthly bill, therefore the total monthly bill is given by

y = 0.4x + 1.25d + 0.75r + u