Use the formula to calculate heat.
[tex]q=m\cdot c\cdot\Delta T[/tex]Where m = 277.0 mg = 0.277g, the variation of the temperatures is from 3.0 °C to 22.0 °C, and q = 12.8 J.
[tex]\begin{gathered} 12.8J=0.277g\cdot c\cdot(22\degree C-3\degree C) \\ 12.8J=0.277g\cdot c\cdot(19\degree C) \\ c=\frac{12.8J}{5.263g\cdot\degree C} \\ c=2.43\cdot(\frac{J}{g\cdot\degree C}) \end{gathered}[/tex]Therefore, the specific heat capacity is 2.43 J/g°C.