Ideal Gas HW Problem: Pressure at 11,000 meters?

[Cuckooforcocoa]

Ideal Gas HW Problem!?

Homework Statement

"At an altitude of 11,000 meters, the air temperature is -50 degrees celsius. The air density is 0.403 kg/m^3. What is the pressure of the atmosphere at that altitude."

Homework Equations

P = P0exp(- Mgy/RT)

The Attempt at a Solution

I attempted to solve the problem using the above equation above equation and my result was P = 2.8 * 10^4. However my online homework is not accepting the answer and I'm not sure what I did wrong. Any help would be greatly appreciated!

 

[ehild]

Po is the pressure at altitude h=0, at the given temperature. I think you used the value given for T=273 K.

Use the Ideal Gas Law instead.

ehild