Suppose that there are 2 million part-time workers and 10 million full-time workers in an economy. Then 400,000 of the part-time workers switch to full-time work. We can conclude that the:

A) official unemployment rate will fall

B) official unemployment rate will rise

C) official unemployment rate will remain unchanged

D) size of the labour force will increase

E) size of the labour force will decrease

Can you give explanation