A biologist is testing a large number of 5ml samples of sea water to estimate the occurrence of a particular micro-organism. She finds that 62% of the samples have at least one micro-organism present. Assuming the microorganisms are randomly occurring, with an average rate of occurrence, a) estimate k, the average number of micro-organisms per sample. b) what is the probability that in the combined sea water of three samples (15ml) she finds more than 2 micro-organisms?