Temperature change time base problem?

Temperature change time base problem. Suppose V = 28 V, I = 0.1 A, mw = 54 gm, cw = 4.18 J/gm K, mr = 10 gm, and cr = 3.7 J/gm K. If the water is initially at room temperature, how long will it take for the water to heat up 2 K? (Hint: dT/dt is approximately equal to T / t .)