$(15\%)$ As shown in below, a shaft with inner radius of $8mm$ turns at $7,500$ RPM inside a stationary journal bearing $40mm$ long. A thin film of oil $0\mathrm{.}3mm$ thick fills the concentric annulus between the shaft and journal. The viscosity of the lubrication oil is $0\mathrm{.}031N\frac{s}{m^2}.$ Please answer the following questions:

$($a$)$ Estimate the torque needed to turn the shaft.

$($b$)$ Estimate the power needed.