At Standard Temperature and Pressure, "STP" (0^(@)"C" and "1 atm"), "1 mole" of any ideal gas occupies 22.4" Liters of Volume".
color(white)(aaaaaaaaaaaaaaaaa)(22.4" L")/(1" mol")
Knowing this, we can think about this for a second without involving any math or calculations.
If we know 1" mole" of a gas occupies 22.4" Liters of volume" at STP, any number of moles more than 1 would occupy more than 22.4" Liters of volume". How much more volume? Well.
color(white)(aaaaaaaaaaaaaaaaa)(1.78 cancel("moles"))/(1 cancel("mole")) = 1.78
This means, there is 1.78"X" more number of moles. So, since we know all else is held constant ("Temperature and Pressure"), "moles" and "Volume" are directly proportional here so "Volume" will increase by the same magnitude ("Avogadro's Law").
1.78 * 22.4" L" = color(blue)(39.87" L"
Answer: 39.87 L