The number of tickets purchased by a computer for a musical performance at a certain concert hall can be considered a random variable. The table below shows the relative frequency distribution for the number of tickets purchased by a customer.
$$ \begin{array}{|r|c|c|c|c|c|} \hline \text{Number of tickets purchased} & 1 & 2 & 3 & 4 & 5 \\ \hline \text{Relative frequency} & 0.20 & 0.45 & 0.10 & 0.20 & 0.05 \\ \hline \end{array} $$Suppose each ticket for a certain musical performance cost $12. Based on the distribution shown, what is the mean cost per customer for the performance?