If the calorimeter whose heat capacity is 110 kJ/°C rises its temperature from 21.2°C to 24.4°C, the heat transmited to it is: 110 kJ/°C * (24.4°C - 21.2°C) = 110kJ/°C (3.2°C) = 352 kJ.
That heat is generated by the combustion of 17.0 g of peanut butter, so the caloric content of it is: 352kJ / 17.0 g = 20.705 kJ/g.
Now use the conversion from kJ to cal:
1 cal = 4.184 J
=> 20.705kJ/g * 1000 J/kJ * 1cal/4.184J = 4948.6 cal/g
Answer: 4948.6 cal/g
