If 10 meter long crane is used to move a rock horizontally at a construction site. when lifting the crane, the cable is continually extended to maintain the rock at the same height with the height of the crane pivot so that the rock moves only horizontally. if the crane is lifted with an angular speed dθ/dt = 1/4 rad/s where θ is an angle between the crane and the ground and t represents time, how fast the rock is moving toward the crane base when the cable is 8 meter