A steel ball of mass 1 kg and specific heat 0.4 kj/kg is at a temperature of 60 deg C. It is dropped into 1 kg of water at 20 deg C. The final steady temperature of water is

A

$$23.48^\circ C$$

B

$$32.28^\circ C$$

C

$$20^\circ C$$

D

$$30^\circ C$$