The cylinder shown is of weight W and radius r. Express in terms XV and r the magnitude of...

The cylinder shown is of weight W and radius r. Express in terms XV and r the magnitude of the largest couple M that can be applied to the cylinder if it is not to rotate, assuming the coefficient of static friction to be (a) zero at A and 0.30 at B, (b) 0.25 at A and 0.30 at B.

Fig. P8.18