Mean and standard deviation of normally distributed waiting times from the percentages in both tails

The times, in minutes, that patients spend in the waiting room of a clinic are normally distributed with mean \(\mu\) and standard deviation \(\sigma\). Records show that \(9\%\) of patients wait longer than \(48\) minutes and \(25\%\) of patients wait less than \(20\) minutes. Find the value of \(\mu\) and the value of \(\sigma\).[6]