Question 4: [4 marks] Bob the repairman classifies his work in two categories: 25% of his repairs are "difficult", the rest being "simple" repairs. The time to complete a difficult repair is assumed to be exponentially distributed with rate 1 = 0.1 and the time to complete a simple repair is assumed to be normally distributed with u = 2 and o2 = 0.25. Knowing Bob has been working for 2.5 hours on the current repair, what is the probability that Bob would qualify it as difficult? Note: You can use any of the following: P(1/2) = 0.6915, d(1) = 0.8413 and P (2) = 0.9772