Need help with Thermochemistry: Someone please check this work

Nitrous Oxide, N20, has a specific heat of 0.88J/gCelsius. Suppose 75.0g of N20 is put into an inflatable balloon. The temperature of the balloon goes from 35C to 16C. The gas is compressed under constant pressure of 1.9atm from 5.1L to 3.4L.

a. Calculate the amount of heat transferred

b. Calculate the amount of work

c. Calculate the overall change in energy

Here is my answer:

a. Amount of Heat is Q= Cm(t1-t2)=0.88*0.75*(35-16)=12.54J

b. W=nRTln(V2/V1). Here n is the mole number of N20. n=0.017, R= 0.08205 L atm/ (mol.K). T=(273+16)=289K

So W=0.017*0.08205*289*ln(3.4/5.1)= -0.16345 J (Negative as work is done against gas)

c. Overall change in energy=12.54J – 0.16345J =