Finding oxygen mass from PV=nRT in a compressed cylinder

[physics4u]

Homework Statement

In a portable oxygen system, the oxygen (O2) is contained in a cylinder whose volume is 0.00260 m3. A full cylinder has an absolute pressure of 1.00e7 Pa when the temperature is 299 K. Find the mass of oxygen in the cylinder.

Homework Equations

PV=nRT

The Attempt at a Solution

So first I solved for n in the PV=nRT eqn, (1.00e7)(.00260)/(8.31)(299K)= 935499.4 moles. After I obtained the Moles I multiplied by avadro's number (6.022e23) to get molecules, and than I multiplied by 1.6605e-27kg/atomic units to get mass. Aparently my answer is incorrect, where did I go wrong for solving this problem?

 

[Shooting Star]

What did you multiply by 1.6605e-27kg/atomic units to get mass? Also remember the molecular weight of O2 is 32.