I need major chem help from a wizard?

3. A sample of tin metal, Sn, initially at 98.7 oC, is dropped into 25.5 g of water at 15.0 oC. When the system comes to thermal equilibrium, the temperature is 19.5 oC. What m (g) of Sn was added? The specific heat capacity of H2O is 4.184 J/g∙K, and Sn 0.227 J/g.K