Amanda and her little brother each throw a model airplane at the same time, but from different heights on the playground. The functions h(x) = -16x2 + 24x + 40 and g(x) = -16x2 + 10x + 21 represent the heights of Amanda's plane and her brother's plane, respectively, x seconds after the planes are thrown.
Which of the following statements is true?
Amanda's brother's model airplane will stay in the air for 3 seconds longer than Amanda's model airplane.
Amanda's brother's model airplane will touch ground 2 seconds earlier than Amanda's model airplane.
Amanda's model airplane will touch ground 4 seconds earlier than Amanda's brother's model airplane.
Amanda's model airplane will stay in the air for 1 second longer than Amanda's brother's model airplane.