Please, I am so stuck on this problem, and it's due really soon. Any work would be appreciated so I can understand this mess.

You begin with 80 g of water at 20 degrees C and 80 g of water at 80 degrees C. After adding the two portions of water into your calorimeter setup and following the procedure outlined in the experiment, you determine the temperature of the mixed portions of water to be 45 degrees C. What is the heat capacity of the calorimeter? (in cal/degrees C)