Compute all parts of given problem:

Problem: A place kicker must kick a football from a point 31.0 m (= 33.9 yd) from the goal, and the ball must clear the crossbar, which is 3.05 m high. When kicked, the ball leaves the ground with a speed of 18.7 m/s at an angle of 51.0o to the horizontal.

Part A: How much does the ball clear the crossbar (if in fact it does)? Enter positive values if the ball clears and negative values if it falls below the crossbar.

Part B: What is the vertical velocity of the ball at the time it reaches the crossbar? Enter positive values if it is still rising and negative values if it is falling.

Please give me an explanation for above problem.