Here, Mass of packet, `M=500g`
volume of the packet, `V=350cm^3`
Clearly, density of packet, `d=(M)/(V)=(500)/(350)=1.428(g)/(cm^3)`
Since the density of packet is more than density of water the packet will sink.
As the packet is fully submerged in water,
mass of water displaced by the packet`=`volume of the packet`xx`density of water