(a) To draw the cumulative frequency graph:

• Calculate the cumulative frequencies: 12, 28, 60, 126, 146, 150.
• Plot these cumulative frequencies against the upper boundaries of the intervals: 4.5, 10.5, 20.5, 30.5, 40.5, 60.5.
• Draw a smooth curve through the points.

(b) To find \(d\) for 30% of journeys:

• Calculate 70% of 150: \(0.7 \times 150 = 105\).
• Find the distance corresponding to a cumulative frequency of 105 on the graph. \(d \approx 27 \text{ km}\).

(c) To calculate the mean distance:

• Find midpoints of each interval: 2.25, 7.5, 15.5, 25.5, 35.5, 50.5.
• Calculate the mean: \(\bar{x} = \frac{(2.25 \times 12) + (7.5 \times 16) + (15.5 \times 32) + (25.5 \times 66) + (35.5 \times 20) + (50.5 \times 4)}{150}\)
• \(\bar{x} = \frac{3238}{150} \approx 21.6 \text{ km}\).