Calorific values of some fuels are given:

Fuel	Calorific value $\left(\mathrm{kJ}/\mathrm{kg}\right)$
Coal	$25000-33000$
Diseal	$45000$
LPG	$55000$
CNG	$50000$

On the basis of this data, find out the correct order of efficiency of fuels.

Different zones of a candle flame are marked by the letters $P,Q,R$   and $S$.
Which of the following statements are correct?
(i) $P$ is the luminous zone and is the hottest part of candle flame.
(ii) In zone $Q$, there is inadequate supply of oxygen.
(iii) Zone $R$ contains unburnt wax vapours produced by melting of wax.
(iv) In $S$ zone, carbon monoxide burns with a blue flame.

Neha took a burning candle and covered it with an empty glass by putting it upside down. She observed that the candle burns for some time before it finally goes off. What is the reason for this?