The mechanism shown in the figure has been employed as a marine steering linkage called a Raphson's slide. O2B represents the tiller and AC is the actuating rod that is pinned to the slider (link 3) which slides along the tiller. If the absolute velocity of the actuating rod (link 4) is 30 cm/s (constant) to the left, find the angular acceleration of the tiller (link 2) in the position shown.