4 In a certain country the time taken for a common infection to clear up is normally distributed with mean \(\mu\) days and standard deviation 2.6 days. \(25 \%\) of these infections clear up in less than 7 days.
- Find the value of \(\mu\).
In another country the standard deviation of the time taken for the infection to clear up is the same as in part (i), but the mean is 6.5 days. The time taken is normally distributed.
- Find the probability that, in a randomly chosen case from this country, the infection takes longer than 6.2 days to clear up.