The acceleration when moving by circle at uniform speed is v^2/r where v is the speed and r is the radius. The direction of acceleration it from the current position towards the center.

Here r = (228*4)/(2pi) approx.= 145.15 (m), v = 228/35 approx= 6.51 (m/s) (as in your answer).

So a = v^2/r approx.= 0.29 (m/s^2).

Now express the direction af acceleration at the point B "counterclockwise the +x-axis". For that, continue the line BO to the upper-left (to some point, denote it B'). Then the angle in question will be COB' and it is clearly counterclockwise (in standard position) and is equal to (180-35) = 145 degrees.