A $1\mathrm{.}20L$ weather balloon on the ground has a temperature of $25\mathrm{.}0C$ and is at atmospheric pressure $(1\mathrm{.}00$atm$).$ When it rises to an elevation where the pressure is $0\mathrm{.}770$atm, then the new volume is $1\mathrm{.}80L.$ What is the temperature $($in $C)$ of the air at this elevation?