I believe it’s A, i could be wrong tho 3
Considering that we are talking about a stepdown transformer, and a turn ration of 1:24
Then
Vsecondary coil = 120 V / 24 = 5V
(But lets remember that the power must be conserved in the transformer, so the voltage is 24 times less, but the current is 24 times higher)
It provides 5 volts to operate the player or charge the batteries
Required Heat = Q
Q = Mass * specific heat of water * change in temp.
Q = 5g * 1g/cal*degC * 20degC
Q = 100 cal of heat is required
To convert calories to Joules,
1 cal = 4.184 Joules
100cal = 418.4 J of heat is needed