Rephrase: The tennis ball reached a maximum height of 50 feet, which is the highest of all the objects. It also took 2.5 seconds to reach the ground, which is shorter than the other objects. This eventuality suggests that the tennis ball was thrown with the most velocity, which is why it reached the highest height and stayed in the air for the shortest amount of time. The fact that Anne is the youngest brother also supports this conclusion. The youngest brother is the fastest of the three brothers, so it makes sense that he would be able to throw the tennis ball the highest and fastest