A thin slab of material of uniform density with a total mass of 3.0 kg is cut in a strange shape: It is bounded by the curve y=4-x2 and x=0. Initially it is lying in the xy plane. It is free to rotate about the y axis. A force of 8.0 Newtons is constantly applied perpendicular to the slab at the outer bottom corner. What angle (in radians) has it rotated through after 20 seconds?