A strip of iron with mass $$15.5\ \text{g}$$ is placed in a solution containing $$21.0\ \text{g}$$ copper sulphate. After some time the reaction stops. Iron strip was found to have mass $$8.5\ \text{g}$$. The mass of copper formed was found to be $$8.60\ \text{g}$$. Find the mass of ferrous sulphate formed in this reaction.

A

$$19.40\ \text{g}$$

B

$$18.40\ \text{g}$$

C

$$17.40\ \text{g}$$

D

$$16.40\ \text{g}$$