Mary is sitting on a bench that is 40 feet from a tall building. Bob walks from the building toward Mary at two feet per second. As Bob approaches, Mary looks at the point of the building directly over Bob's head. Bob's head is three feet higher than Mary's eyes. a). At what rate is the point on the building that Mary looks at rising when Bob is four feet from Mary? b). As Bob gets closer, the angle of elevation of Mary's eyes (the angle between Mary's line of vision and a horizontal line through her eye) increases. At what rate is the angle of elevation increasing when Bob is four feet from her?