Simple sums

I want someone to solve these two sums. I will pay $2 for each sum. Need it as soon as possible 1. A man goes to see his medical doctor to find out whether or not he has a deadly disease. The test is positive. The test is 95% accurate and one in one thousand men of his age has this disease. What is the probability he has the disease? He decides to seek a second opinion but the results are exactly the same. When this question was put to a group of doctors, 80% of them answered “95%”. He now plans to sell up all his assets, tell his boss what he really thinks of her, quit his job on the spot and live in Fiji in the time he has left. Is this a rational decision? Explain. 2. Suppose an urn contains 100 marbles, 75 red and 25 black. A marble is drawn at random from the urn and you are asked to guess what colour you believe the marble to be. The marble is then shown, replaced, and the urn's contents again randomised. The aim is to maximise the number of correct guesses. Before reading any further, what strategy would you employ? What would you guess? Assume 4 red come out in a row. What would your next guess be? Why? Include a brief discussion of the gambler's fallacy.