Use lewis symbols to represent the reaction that occursbetween
mg and br atoms.

Explanation:

The electronic configuration of magnesium with Z = 12 is : 2, 8, 12

The electronic configuration of bromine with Z = 35 is : 2, 8, 18, 7

The Lewis structure is drawn in such a way that the octet of each atom is complete.  

Thus, magnesium losses two electrons to bromine and 2 atoms of bromine accepts the electron.

Thus, the valence electrons are shown by dots in Lewis structure. The reaction is shown in image below.

93.2 ml + 3920 ml = 4013 ml total  

(93.2 ml) * (2.03 m) / (4013 ml) = 0.0471 m

the volume in in l of the diluted solution would be 0.0471 m.