Stephanie sells 12 pretzels per hour. Robert sells 15 pretzels per hour. This week, Robert sold an additional 18 pretzels. Which of the following expressions represent the total sales of both people in this week, where S represents Stephanie worked and R represents the number of hours that Robert worked?


A- 15S + 12R +18
B- 12S + 15R +18
C- 12S + 15R
D- 12S + 18R