A dimensionally consistent relation for the volume V of a liquid of coefficient of viscosity (η) flowing per second through a tube of radius (r) & lenght (l) & having a pressure (P) across its end is

a. V = π pr⁴ / 8ηl

b. V = π ηl / 8pr⁴

c. V = 8pηl / π r⁴

d. V = π pη / 8lr⁴

I know its kindda late and its not accurate method but here it is....Since the length and the radius have same dimensions this question can`t get solved by dimensional method. So you should put the dimensions of all quantities in each option. The option which will give you `L cube` dimension will be the correct one.