An ideal gas is taken once round the cycle A to B to C to A shown in the figure. From A ($10\ \text{L}$, $2.0\ \text{bar}$) it expands at constant pressure to B ($30\ \text{L}$), then its pressure falls at constant volume to C ($1.0\ \text{bar}$), and it returns to A along the straight line CA. Take $1\ \text{L bar} = 100\ \text{J}$. How much heat $q$ does the gas take in over one cycle?

Fig. 1: A pressure-volume graph of a cycle. Point A is at 10 L and 2.0 bar, point B at 30 L and 2.0 bar, and point C at 30 L and 1.0 bar. Arrows run from A to B along the line of constant pressure, from B down to C along the line of constant volume, and from C back to A along a straight sloping line, so the cycle encloses a right-angled triangle.