(4) A mining company is carrying out a survey in a region of Western Australia. On the basis of preliminary results, the company’s senior geologist estimates that there is a 60% probability that a particular mineral will be found in quantities that would justify commercial investment in the region. Further research is then carried out and this suggests that commercially viable quantities of the mineral will be found. It is estimated that this research has a 75% chance of giving a correct indication. Revise the senior geologist’s prior probability in the light of the research results.