A scientist is studying the cell cycle of onion root tip meristem cells (Allium cepa), where one complete cycle takes 20 hours.
Figure 1 shows the relative proportion of time spent in each of the three stages of this cell cycle (Stage X, Stage Y, and Stage Z).
a.[2]
What percentage of the total time of the cell cycle is spent in Stage X?
b.[3]
If a sample starts with 2 active meristematic cells, and each divides to form two new cells every 20 hours, how many hours will it take for this sample to reach a total of 64 cells?