Jim and his dad are building a rectangular flower bed. They have a total of 35 feet of landscaping timber to use, and they want to use all of it. However, they are not sure what width and length they want the flower bed to be. In this activity, you will write a function in which the width of the flower bed, w, is the input, and the length, l, is the output. The perimeter of a rectangle is given by the equation 2l + 2w = p. If the width of the flower bed is 15 feet, what is its length? Write your answer as an evaluation of a function.