Scott is putting money into a savings account. He starts with $350 in the savings account, and each week he adds $40. Let S represent the total amount of money in the savings account (in dollars), and let W represent the number of weeks Scott has been adding money. Write an equation relating S to W. Then use this equation to find the total amount of money in the savings account after 18 weeks. Equation: Total amount of money after 18 weeks: $