The following table gives the literacy rate (in percentage) of 35 cities. Find the mean literacy rate.\begin{array}{|c|c|c|c|c|c|} \hline \text{Literacy rate (in \%)} & 45 - 55 & 55 - 65 & 65 - 75 & 75 - 85 & 85 - 95 \\ \hline \text{Number of cities} & 3 & 10 & 11 & 8 & 3 \\ \hline \end{array}