It is believed that the relationship between / and t can be expressed in the form N = ab' where a and b are constants. Explain how this can be tested by plotting log N against t. [2] Make out a table of values of log / and draw the graph. [3] Use your graph to estimate the values of a and b. [3] Estimate the number of bacteria present after 20 days. State, with a reason, whether your estimate is likely to be a good one. [2]