Read the excerpt from Team Moon. The heavier the spacecraft, the harder it is to launch. And fuel is heavy. So it was critical to pinpoint the fuel needed, add a cushion, then take no more than necessary. But now, because the landing was taking far longer than planned, the fuel was almost gone. Mission Control wanted Neil to take as much time as he needed and fly the LM as near empty as possible only because they wanted him to make the landing. But if he ran out of fuel above the surface, in all likelihood the LM would crash onto the moon. So they were trying to time it to the last possible second before calling an abort—calling off the landing. Why does the author use a problem-solution text structure in the paragraph?