The final volume : 3.4 L
Charles's Law
When the gas pressure is kept constant, the gas volume is proportional to the temperature
[tex]\tt \dfrac{V_1}{T_1}=\dfrac{V_2}{T_2}[/tex]
V₁=3300 ml
T₁=63 + 273=336 K
T₂=78+273=351 K
the final volume :
[tex]\tt V_2=\dfrac{V_1.T_2}{T_1}\\\\V_2=\dfrac{3300\times 351}{336}\\\\V_2=3447.3~ml\rightarrow 2~sig.~fig.\rightarrow 3.4~L[/tex]