A Sliding contact bearing is operating under stable condition. The pressure developed in oil film is p when the journal rotates at N r.p.m The dynamic viscosity of lubricant is $\mu$ and effective coefficient of friction between bearing and journal of diameter D is f. which one of the following statements is correct for the bearing?
(a) f is directly proportional to $\mu$ and P
(b) f is directly proportional to $\mu$ and N
(c) f is inversely proportional to p and D
(d) f is directly proportional to $\mu$ and inversely proportional to N