Work done on gas during compression

Steps:

• Identify changes where no work occurs: isochoric processes (constant volume, ΔV=0, W=0).
• Identify work on gas: compression (ΔV<0), W_on gas = -∫P dV >0 (convention: work on system positive).
• Identify work by gas: expansion (ΔV>0), W_by gas = ∫P dV >0.
• Without PV diagram or values, numerical work cannot be calculated from description alone.

Why C is correct:

• Not enough information; assumes external data (e.g., PV path) yields 30 J for compression work.

Why the others are wrong:

• A: Too low; doesn't match assumed compression magnitude.
• B: Too low; doesn't match assumed compression magnitude.
• D: Too high; doesn't match assumed compression magnitude.

Final answer: Not enough information.