4-21. A football is placed on a line 25 m from the goalpost. The placement kicker kicks the ball directly toward the goalpost, giving it a velocity of 21.0 m/s at an angle of 47.0^o above the horizontal. The horizontal bar of the goalpost is 3.0 m above the field. How far above or below the horizontal bar of the goalpost will the ball travel?

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We must choose a coordinate system in which to solve the problem. Which is best?

(A)
(B)
(C)
(D)