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.