A solid sphere is placed rotating with its center initially at rest in a corner as shown. (a) and (b) . Coefficient of friction between all surfaces and sphere is $\large\frac{1}{3}$ Find the ratio of friction forces $\large\frac{fa}{fb}$ by ground in situations (a) and (b)

Question

 

\[\begin {array} {1 1} (a)\;1 & \quad (b)\;\frac{9}{10} \\ (c)\;\frac{10}{9} & \quad  (d)\;none\;of\;these \end {array}\]