Nitrogen gas from decomposition problem. Please show how to do this?

Molar mass of (NH₄)₂Cr₂O₇ = (14.0×2 + 1.0×8 + 52.0×2 + 16.0×7) g/mol = 252.0 g/mol
No. of moles of (NH₄)₂Cr₂O₇ decomposed = (100.0 g) / (252.0 g/mol) = 0.3968 mol
No. of moles of N₂ produced = (0.3968 mol) × (1/1) = 0.3968 mol

Consider the N₂ produced:
Pressure, P = (757/760) atm
Volume, V = ? L
No. of moles, n = 0.3968 mol
Gas constant, R = 0.0821 L atm / (mol K)
Temperature, T = (273 + 22) K = 295 K

Gas law: PV = nRT
Hence, V = nRT/P
Volume of N₂ produced = 0.3968 × 0.0821 × 295 / (757/760) L = 9.65 L (to 3 sig. fig.)