A centrifuge is processing 1000 litres per hour of water containing 2 g per litre of suspended solids. The thickened slurry coming out of the centrifuge has solids concentration of $20 \mathrm{~g}$ per $100 \mathrm{ml}$. If the centrifuge has $99 \%$ efficiency based on solids separation, the flow rate (in litres per hour, rounded off to one decimal place) of the supernatant stream will be___________
