(i) The work done by the weightlifter is calculated using the formula for gravitational work done:

\(WD = mgh\)

where \(m = 200 \text{ kg}\), \(g = 9.8 \text{ m/s}^2\), and \(h = 0.7 \text{ m}\).

Substituting the values, we get:

\(WD = 200 \times 9.8 \times 0.7 = 1400 \text{ J}\)

(ii) The average power developed is calculated using the formula:

\(\text{Power} = \frac{\text{Work Done}}{\text{Time}}\)

Substituting the values, we get:

\(\text{Power} = \frac{1400}{1.2} = 1166.67 \text{ W}\)

Rounding to the nearest whole number, the average power is \(1170 \text{ W}\).