$A$ carrier wave $60 \sin(2\pi \times 10^6 t)$ is modulated by a signal $15 \sin(300\pi t)$. The modulation index is: (in $\%$)

In amplitude modulation,

If a number of sine waves with modulation indices $n_1, n_2, n_3, \dots$ modulate a carrier wave, then the total modulation index $(n)$ of the wave is:

The attenuation in optical fibre is mainly due to

If the highest modulating frequency of the wave is $5\, kHz$,the number of stations that can be accommodated in a $150\, kHz$ bandwidth are

$A$ transmitting antenna can cover an area of $6.4\pi \times 10^9 \ m^2$ when used for broadcasting. If the signal is transmitted to another antenna,which is at a distance of $100 \ km$ from this antenna,what should be the minimum height of the receiving antenna for satisfactory communication in line-of-sight mode (in $m$)? (Assume the radius of the Earth $R = 6400 \ km$)