Answer
The mass flux through the surface is $~~693~kg/s$
Work Step by Step
We can find the mass flux through the surface:
$mass~flux = \rho~w~d~v$
$mass~flux = (1000~kg/m^3)(3.22~m)(1.04~m)(0.207~m/s)$
$mass~flux = 693~kg/s$
The mass flux through the surface is $~~693~kg/s$