On recrystallization, 20g of magnesium tetraoxosuphate (IV) forms 41 g of magnesium tetraoxosulphate (IV) crystals, MgSO₄. yH₂O. The value of y is?

(Mg = 24, S = 32, O = 16, H = 1)

• A.1
• B.3
• C.5
• D.7
• E.