[填空题]
A person exerts a force 5l 8r.. ppkm3q2hthgu of 55udw gii2/-wn 3 N on the end of a door 74 cm wide. What is the magn3i d-wun/g i2witude of 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? $m \cdot N$