So you know the ideal gas law
PV = nRT
well R is a constant, Pressure is given to be constant and of course the moles, n are constant.
What is left is direct variation.
Initial temp and volume
V = kT
final temp and volume
v = kt
crate a ratio, I think this is called charles law
V/v = T/t
4 / 9.840 = 7.836x10 / t
solve for final temp, will be in Celsius since T is in Celsius
** round answer to 4 significant figures..
t = (78.36 * 9.84 ) / 4
t = 192.8 C