[填空题]
A person exerts a force of 55 N on the end of a door 74 cm 9 yyjg2j:c1 mfa4zvy 9wide rp1ezmf04 p2p+qvzi8v7;dtn . What is the magnitude o1 p+74r8d 2pzf;vtei pnqv0 zmf the torque if the force is exerted (a) perpendicular to the door $m \cdot N$ (b) at a 45 $^{\circ} $ angle to the face of the door? $m \cdot N$