Answer
$2.4\frac{Kg}{s}$
Work Step by Step
We can find the flow rate as
$\frac{\Delta m}{\Delta t}=\rho(\frac{\pi d^2}{4})v$
We plug in the known values to obtain:
$\frac{\Delta m}{\Delta t}=\frac{1000}{\frac{\pi(0.038)^2}{4}}(2.1)=2.4\frac{Kg}{s}$