Suppose a country has a population of 120 people, a working-age population of 100 people, its labor force participation rate is XXXXXXXXXX%), and the quantity of output is 60 units. Suppose that the...

Suppose a country has a population of 120 people, a working-age population of 100 people, its labor force participation rate is 0.5 (50%), and the quantity of output is 60 units. Suppose that the production function of the economy is given by Y=2N, where Y represents the quantity of output and N represents the number of workers needed to produce the output.

I know the answer is 0.4 but I don't understand how to get it. Thank you!