Magnetic field at the centre of a circular loop of area ' $A$ ' is ' $B$ '. The magnetic moment of the loop will be

A wire of length ' $L$ ' and linear density ' $m$ ' is stretched between two rigid supports with tension ' $T$ '. It is observed that wire resonates in the $\mathrm{P}^{\text {th }}$ harmonic at a frequency of 320 Hz and resonates again at next higher frequency of 400 Hz . The value of ' $p$ ' is