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.