Im studying for the Fundamentals of Engineering exam (coming up April 12!!) and came across this Thermodynamics problem in my review book.

So the work for an isothermal process is RT_{A}*ln(V_{B}/V_{A}), where V_{A} was previously determined to be 0.103m^{3}.

In the solution to the problem, the RT_{A} term is replaced with P_{A}*V_{A}, where it should be (P_{A}*V_{A})/n from the ideal gas law.

Is this solution wrong? As I see it, this cant be solved without knowing the number of moles of gas (or mass of the gas depending on which R is used). I was unable to get the correct answer, and the solution seems wrong to me.