We use the formula:
PV = nRT
First let us get the volume V:
volume = 14 ft * 12 ft * 10 ft = 1,680 ft^3
Convert this to m^3:
volume = 1680 ft^3 * (1 m / 3.28 ft)^3 = 47.61 m^3
n = PV / RT
n = (1 atm) (47.61 m^3) / (293.15 K * 8.21x10^-5 m3 atm / mol K)
n = 1,978.13 mol