(i) To draw the cumulative frequency graph, calculate the cumulative frequencies:

Plot these points and join them with a smooth curve.

(ii) 28% of the daffodils are of height \(h\) cm or more, which means 72% are less than \(h\). 72% of 200 is 144, so \(h\) corresponds to the cumulative frequency of 144. From the graph, \(h \approx 22.5 \text{ cm}\).

(iii) To calculate the standard deviation:

Use the midpoints of the intervals: \(7, 13, 18, 23, 28\).

Calculate the variance:

\(\text{var} = \frac{(7^2 \times 22 + 13^2 \times 32 + 18^2 \times 78 + 23^2 \times 40 + 28^2 \times 28)}{200} - 18.39^2\)

\(= \frac{74870}{200} - 18.39^2\)

\(= 374.35 - 18.39^2\)

\(= 36.1579\)

Standard deviation \(\text{sd} = \sqrt{36.1579} = 6.01\).