Mass flow rate of a fluid with non-uniform density

Classical Mechanics

A strange fluid completely fills the pipe of radius $r = 1\text{ m}$ through which it flows with speed $v = \frac{1}{2-\ln 3} \frac{\text{m}}{\text{s}}.$ If the density varies radially according to $\rho(r) = \frac{1000}{\pi (1 + 2r)},$ what is the mass flow rate in $\frac{\text{kg}}{\text{s}}?$