What is the frequency of an $FM$ transmitter without a signal input?

If $f_a$ and $f_f$ represent the carrier wave frequencies for amplitude and frequency modulations respectively,then

In satellite communication,the $6\,\text{GHz}$ frequency is used for........... and the $4\,\text{GHz}$ frequency is used for...........

The number of amplitude modulated broadcast stations that can be accommodated in a $300\, kHz$ bandwidth for the highest modulating frequency of $15\, kHz$ is:

$A$ message signal of frequency $8 \text{ kHz}$ and peak voltage $12 \text{ V}$ is used to modulate a carrier of frequency $1.2 \text{ MHz}$ and peak voltage $20 \text{ V}$. The modulation index is

Assertion $(A)$: Television signals are received through sky-wave propagation.
Reason $(R)$: The ionosphere reflects electromagnetic waves of frequencies in the range $(3-30)$ $MHz$.
Choose the correct option.