帮忙看看这样做对么？

Xiaotongdi

题目是说一个机器seal k cartons用8小时，另一个机器k用4小时，如果两个机器working at its own constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate?
a. 25%
b. 33.3%
c. 50%
d. 66.6%
e. 75%
这题我现在会做，但是刚看这题时在那个翻译上，尤其是说两个机器用各自的速度，用同样的时间做工，那个同样的时间是指8小时么？还是什么时间？