15. A medieval prince trapped in a castle, in a valley, wraps a message around a rock and throws it from the top of the castle wall with an initial velocity of 40.0 m/s [30 above the horizontal]. The rock lands just on the far side of the castle's moat, on the way down, at a level 10.0 m above the initial level. Draw a digram of situation. Determine the width of the moat and velocity of impact. [10]