If $E_c$ and $E_m$ are peak values of carrier and modulating signals,respectively,then for $100 \%$ modulation,

In an $AM$ wave,the total power is $900 \ W$. For $100\%$ modulation,the power transmitted in the sidebands is ... $W$.

What is the bit rate in $bits/sec$ for a signal with $16$ quantization levels and a sampling rate of $8 \, kHz$?

We do not transmit low frequency signals to long distances because:
$(a)$ The size of the antenna should be comparable to signal wavelength,which is impractical for a signal of longer wavelength.
$(b)$ Effective power radiated by a long wavelength baseband signal would be high.
$(c)$ We want to avoid mixing up signals transmitted by different transmitters simultaneously.
$(d)$ Low frequency signals can be sent to long distances by superimposing them with a high frequency wave.
Therefore,the most suitable options are:

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

$A$ message signal of frequency $10 kHz$ is used to modulate a carrier wave of frequency $6 MHz$. The sideband frequencies are: