Mass of water = 72 g = 72 /1000 = 0.072 kg
Temperature rise = 80°C
Heat gained = mcθ
Where m = mass in kg, c is specific heat capacity of water = 4200 J/kg°C
θ = Temperature rise.
Heat gained = mcθ
= 0.072 * 4200 * 80 = 24192
So heat needed = 24 192J.