A college Professor classifies his students according to their grade point average (GPA) and their class rank. GPA is on a 0.0-4.0 scale, and class rank is defined as the under class (freshman and sophomores) and the upper class ( juniors and seniors). One student is selected at random. The table below provides joint probabilities.
GPA
2.5or less Above 2.5
Under Class 0.22 0.15
Upper Class 0.12 ?
If selected student has a GPA above 2.5 what is the probability that they are upper class?