The triple point of water is

Two thermometers are used to record the temperature of a room. If the bulb of one is wrapped in a wet hanky,which of the following statements is correct?

$A$ constant volume gas thermometer shows pressure readings of $50 \, cm$ and $90 \, cm$ of mercury at $0^{\circ} C$ and $100^{\circ} C$ respectively. When the pressure reading is $60 \, cm$ of mercury,the temperature is ......... $^{\circ} C$.

Is negative temperature possible on the Kelvin scale? Why?

Answer the following:
$(a)$ The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong with taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?
$(b)$ There were two fixed points in the original Celsius scale as mentioned above,which were assigned the numbers $0^{\circ}C$ and $100^{\circ}C$ respectively. On the absolute scale,one of the fixed points is the triple-point of water,which on the Kelvin absolute scale is assigned the number $273.16\; K$. What is the other fixed point on this (Kelvin) scale?
$(c)$ The absolute temperature (Kelvin scale) $T$ is related to the temperature $t_c$ on the Celsius scale by $t_c = T - 273.15$. Why do we have $273.15$ in this relation,and not $273.16$?
$(d)$ What is the temperature of the triple-point of water on an absolute scale whose unit interval size is equal to that of the Fahrenheit scale?

The triple points of neon and carbon dioxide are $24.57\; K$ and $216.55\; K$ respectively. Express these temperatures on the Celsius and Fahrenheit scales.