For this question, we need the formula τ = F x d, and just plug the numbers in.
Given the formula τ = F x d
Where τ = torque,
F = force applied, &
d = distance from the axis / hinge,τ = 300 c 0.8 = 240NmDisregard the weight of the door or if there's any friction at the hinge. None of this will change the torque applied.