The nucleus ${ }_{50}^{120} X$ undergoes the series of reactions given below:

$$ { }_Z^A X \xrightarrow{\alpha \text {-decay }} P \xrightarrow{\beta^{-} \text {-decay }} Q \xrightarrow{\alpha \text {-decay }} R $$

The number of neutrons in the nucleus $R$ is

In the logic circuit given below, if $X=1$ and $Y=1$, then the values of $P, Q$ and $R$ are

The symbol given below represents

A telephonic communication service is working at a carrier frequency of 20 GHz . Only $20 \%$ of it is utilised for transmission. If each channel requires a bandwidth of 5 kHz , then the number of telephonic channels that can be transmitted simultaneously are