[填空题]
A person exerts a force of 55jq6j(, :afavfxjq3th1 c vf4* N on the end of a door 74 cj yd:nk3vj cjx/3b(6nm wide. What is the magnitude of the torque if the force is exey3j:6j3dj/ kc (xnnbvrted (a) perpendicular to the door $m \cdot N$ (b) at a 45 $^{\circ} $ angle to the face of the door? $m \cdot N$