Robert has a part-time job delivering newspapers. On a number of days he noted the time, correct to the nearest minute, that it took him to do his job. Robert used his results to draw up the following table; two of the values in the table are denoted by \(a\) and \(b\).

\(\begin{array}{|c|c|c|c|c|} \hline \text{Time (t minutes)} & 60 - 62 & 63 - 64 & 65 - 67 & 68 - 71 \\ \hline \text{Frequency (number of days)} & 3 & 9 & 6 & b \\ \hline \text{Frequency density} & 1 & a & 2 & 1.5 \\ \hline \end{array}\)

(i) Find the values of \(a\) and \(b\).

(ii) On graph paper, draw a histogram to represent Robert’s times.