From the calculations, the specific heat capacity of diamond is 42.36  J/Kg/°C.
The specific heat capacity is the heat absorbed or emitted when 1Kg of a susbtance is heated such that its temperature is increased by 1 K.
Now;
Mass of water = 26.05 g or 0.026 Kg
Mass of diamond = 2.05 g or 0.00205 Kg
specific heat capacity of water = 4200 J/Kg/°C
specific heat capacity of diamond = ?
Initial temperature of water =  27.20°C
Initial temperature of diamond =74.21 °c
Final temperature of the diamond and water = 27.65 °c
Heat lost by diamond = heat gained by water
mcdT = mcdT
0.00205 Kg * c * ( 74.21 °c - 27.65 °c ) = 0.026 Kg * 4200 J/Kg/°C * (27.65 °c - 27.20°C)
0.116c = 4.914
c = 4.914/0.116
c = 42.36  J/Kg/°C
Learn more about specific heat capacity: https://brainly.com/question/2530523