Potential energy at height h is mgh. Heat generated Q = (1/2)mgh. Also, Q = mcΔT, where c is the specific heat of water (4200 J/kg°C). So, mcΔT = (1/2)mgh. ΔT = gh / (2c) = (9.8 * 84) / (2 * 4200) ≈ 0.098°C, which is closest to 0.1°C.