A cup of coffee cools from 90$$^\circ$$C to 80$$^\circ$$C in t minutes, when the room temperature is 20$$^\circ$$C. The time taken by a similar cup of coffee to cool from 80$$^\circ$$C to 60$$^\circ$$C at a room temperature same at 20$$^\circ$$C is :

Match Column - I and Column - II and choose the correct match from the given choices.

	Column - I		Column - II
(A)	Root mean square speed of gas molecules	(P)	$${1 \over 3}nm{\overline v ^2}$$
(B)	Pressure exerted by ideal gas	(Q)	$$\sqrt {{{3RT} \over M}} $$
(C)	Average kinetic energy of a molecule	(R)	$${5 \over 2}RT$$
(D)	Total internal energy of 1 mole of a diatomic gas	(S)	$${3 \over 2}{k_B}T$$

The average thermal energy for a mono-atomic gas is : (k_B is Boltzmann constant and T absolute temperature)

The mean free path for a gas, with molecular diameter d and number density n can be expressed as :