How would you calculate her return on investment (ROI) to help her understand the benefit of using AdWords?

Your client‟s product costs UD$50 to produce, and it sells for US$150. She‟s sold 10 units and spent US$700 on her AdWords campaign. How would you calculate her return on investment (ROI) to help her understand the benefit of using AdWords?

A) [US$150 (sales price) – US$1500 (cost)] / US$700 (AdWords spend)
B) [US$1500 (revenue) – US$1200 (cost + AdWords spend)] / US$1200 (cost + AdWords spend)
C) [US$1500 (revenue) – 10 (number of prroducts sold)] / US$1200 (cost + AdWords spend)
D) US$1500 (revenue) / US$1200 (cost + AdWords spend)