A centrifugal filtration unit operating at a rotational speed of w has inner surface of the liquid $($density L$)$ located at a radial distance R from the axis of rotation. The thickness of the liquid film is and no cake is formed. The initial pressure drop during filtration is

w$2.$ R$2.$ L

w$2.2.$ L

w$2.$ L $(2$R $+)$

w$2.$ R $.$ L$($R $+2)$