A homogeneous, incompressible, steady ocean of mixed layer depth of $20$ m has a velocity gradient $-5 \times 10^{-8} \mathrm{~s}^{-1}$ and $-8.3 \times 10^{-8} \mathrm{~s}^{-1}$ along zonal and meridional directions, respectively. The vertical mass flux $\text{(in $\mathrm{kg} \mathrm{s}^{-1}$ )}$ at the base of the mixed layer of $100 \mathrm{~km} \times 100 \mathrm{~km}$ area is __________ is $1025 \mathrm{~kg} \mathrm{~m}^{-3}$ ). $\text{(Rounded off to 1 decimal place)}$
