(i) To calculate the mean, use the midpoints of each interval:

Mean = \(\frac{(2.5 \times 11 + 7.5 \times 20 + 15 \times 32 + 25 \times 18 + 35 \times 10 + 55 \times 6)}{97} = 18.4\) minutes.

To calculate the standard deviation, use:

\(\text{sd} = \sqrt{\frac{(2.5^2 \times 11 + 7.5^2 \times 20 + 15^2 \times 32 + 25^2 \times 18 + 35^2 \times 10 + 55^2 \times 6)}{97} - \text{mean}^2}\) = \(13.3\) minutes.

(ii) To draw the histogram, calculate the frequency densities:

• 0 ≤ t < 5: \(\frac{11}{5} = 2.2\)
• 5 ≤ t < 10: \(\frac{20}{5} = 4.0\)
• 10 ≤ t < 20: \(\frac{32}{10} = 3.2\)
• 20 ≤ t < 30: \(\frac{18}{10} = 1.8\)
• 30 ≤ t < 40: \(\frac{10}{10} = 1.0\)
• 40 ≤ t < 70: \(\frac{6}{30} = 0.2\)

Plot these frequency densities against the time intervals on the histogram.