Two half lives so it is 4000 years old
Speed of wave is given as

Wavelength of the wave is given as

now from the formula of wave time period we can say




so it will have time period of T = 4 s
It is an imaginary transformer which has no core loss, no ohmic resistance and no leakage flux. The ideal transformer has the following important characteristic. The resistance of their primary and secondary winding becomes zero. The core of the ideal transformer has infinite permeability.
The answer is that FRICTION PRODUCES HEAT.