The graph below shows the growth of a population of Chlorella vulgaris (a photosynthetic microalga) in a bioreactor over a period of 24 hours.

To compare the rates of division at different times during this growth cycle:
Estimate the rate of division at t=8t = 8t=8 hours by finding the gradient of the tangent line at t=8t = 8t=8.
Estimate the rate of division at t=16t = 16t=16 hours by finding the gradient of the tangent line at t=16t = 16t=16.
Calculate how many times faster the rate of division is at t=8t = 8t=8 hours than at t=16t = 16t=16 hours.