(i) Using Newton's second law, the net force on the car is given by:

\(F = ma\)

where \(m = 700 \text{ kg}\) and \(a = 2 \text{ m s}^{-2}\).

The driving force \(DF\) minus the resistance force equals the net force:

\(DF - 600 = 700 \times 2\)

\(DF - 600 = 1400\)

\(DF = 1400 + 600 = 2000 \text{ N}\)

(ii) The power \(P\) is given by:

\(P = Fv\)

where \(F = 2000 \text{ N}\) and \(v = 15 \text{ m s}^{-1}\).

\(P = 2000 \times 15 = 30000 \text{ W}\)

Thus, the rate of working is 30000 W or 30 kW.