Two students each carry a box up to the third ﬂoor of a building. The total mass of each student and the box she is carrying is the same. Roberta makes the
trip in 45 s while Mary takes 30 s. Which of the following statements best describes this task?
A. Roberta does more total work than Mary.
B. Mary does more total work than Roberta.
C. Roberta has a greater power output than Mary.
D. Mary has a greater power output than Roberta.