3) C

Resultant force = 900N – 600N = 300N upwards

Direction would be upwards as the drag force (upward force) is greater than weight (downward force).

We know that Force = mass x acceleration; Acceleration = Force/Mass

Force = 300N
Mass = 60kg (given in question)
Acceleration = Force/Mass = 300/60 = 5 m/s²