The time taken by Smith to travel from A to B is a random variable which follows the normal distribution , with mean 5 minutes and standard deviation 1 minute. The time taken by Jones to travel from A to B follows the normal distribution with mean 15 minutes and SD 2 minutes and is independent of the time taken by Smith. Smith and Jones start to move from A to B at the same time. Smith takes only 4 minutes to reach B and then he returns to A. Determine, up to 3 significant figures the probability that Smith will return to A after Jones arrive at B.
The Attempt at a Solution
Do i calculate the probability that Jones take less than 4 mins to reach B? If so, the probability is simply 0 so this is wrong.
Or do i take this as a conditional probability question since Jones is known to have arrived at B? If so, i am stucked here.