Adiabatic Expansion of a Gas: Final Pressure-Volume Product Calculation

[vetgirl1990]

Homework Statement

A gas consisting of diatomic molecules that can rotate but not oscillate at a given range of temperatures expands adiabatically from pressure of 365Pa and volume of 70m³, doing 101J of work, while expanding to a final volume. What is its final PV (pressure volume) product?

Homework Equations

For an adiabatic expansion:
W = (1/ϒ-1)(p_fv_f - p_iv_i)

The Attempt at a Solution

i) Degrees of freedom: 3
Therefore, ϒ=1.4

ii) Plug and chug of the equation above.
W = (1/ϒ-1)(p_fv_f - p_iv_i)
101 = (1/1.4-1)(p_fv_f - 365*70)
101 = 2.5p_fv_f - 63875
p_fv_f = 25590 Pa / m³

I'm fairly certain I found the degrees of freedom correctly, and the latter part of my calculations is pretty straightforward... Still getting the wrong answer, however. Chance that the answer is wrong? Or am I approaching the problem incorrectly?

 

[haruspex]

Isn't it 3 degrees of freedom for a monatomic gas?