How to find specific heat of a turpentine question?

Using the fomrula 
\[m_1 (T_{f}-T_{in}) C_1=-m_2 (T'_{f}-T'_{in})C_2,\]
Here $T_f, T'_f$ represents the final tempreture and $T_{in}, T'_{in}$ represents the initial tempreture of the two materials, $C_1, C_2$ are the specific heat constants. Substitunig the given information we have
\[76.8 (31.9-86.5) \times 0.092=- 68.7 (31.9-19.5)C_2\]
\[\Rightarrow -385.78176=-851.88C_2\]
\[\Rightarrow C_2= \frac{-385.78176}{-851.88}=0.452859 .\]
So the specific heat of the turpentine is 0.452859 cal/g ⁰C.