A beat is an interference pattern between two sounds of slightly different frequencies, perceived as a periodic variation in volume whose rate is the difference of the two frequencies. Frequency beat is equal to,

The reference frequency in our case would be 392Hz, and since there is the possibility of the upper and lower range for the amount of beats per second that the two possible frequencies are heard would be


Therefore the two possible frequencies the piano wire is vibrating at, would be 396Hz and 388Hz
Here in nuclear reaction we can say that sum of neutrons and protons in reactant side and product side will be same always
Here mass number on the product side is given to us
so sum of mass number is given as

now on the reactant side also the number must be same

now we will have


Now number of protons on product side is given as

now we also know that atomic number of Fe is 26
so now we will have



now the equation is given as

Answer: the first law of thermodynamics
Explanation: