The square plate is attached to a short link at A and a roll

The square plate is attached to a short link at A, and a roller at C. At the instant shown, the control link OA has a counterclockwise angular velocity of 4 rad/s. If the speed of point C is slowing down at the rate of 50 mm/s^2, determine the acceleration of point A and B at this instant.

Solution

Ocean water, just below the topmost layer (where reflection back to the sky and a complex mechanism of heat transfer and evaporation mass transfer occurs) receives 65 W/m2 of solar energy in one locality. The extinction coefficient is 0.4 m-1. calculate (a) the volumetric heat-generation rate q\'\'\', in watts per cubic meter, near the surface and 1 m below the surface, and (b) the distance below the surface, in meters, where 99.99 percent of solar energy has been absorbed.

I am having trouble with the second part of part A (1m below the surface) and part B.