Answerer: Darrell has already donated $23 to the foundation, so f (0) =$23.
Because x represents the number of weeks, and Darrell is contributing $1 every day, Monday through Friday, he will contribute a total of $5 per week. So, the total amount donated will increase by $5 each week. Therefore, the recursive function will be f (x) =f(x - 1) + $5, where f ($23).