The diagram illustrates the labour demand and labour supply curves for a firm. The starting wage rate is shown by $W_0$ and the equilibrium quantity of labour employed is $L_0$. A trade union representing all of the workers negotiates an increase in the wage rate to $W_1$. What amount of unemployment is caused by this rise in wages?
- A$OL_1$
- B$L_0L_2$
- C$L_1L_0$
- D$L_1L_2$