Answer
$5.99\ g$
Work Step by Step
From Henry's Law and assuming that the soda's density is 1 kg/L
$\Delta S=k_H\times(P_{in}-P_{out})=0.034\ mol/kg.bar\times(4.0-3.7\times10^{-4})bar=0.136\ mol/kg$
$0.136\ mol_{CO_2}/kg_{soda}\times1.0\ L_{soda}\times 1.0\ kg/L|_{soda}\times 44.01\ g/mol|_{CO_2}=5.99\ g$
