specific heat capacity for water = 4.18 Joules/(gram*degreeCelcius)
(how much energy is required per gram per change in degrees C)

mass = 4g
Change in temperature = 6 degC

energy required = mass * change in temperature * specific heat capacity
= 4g * 6 degC * 4.18 J/(g*degC)
= 100.32 Joules