A country's birth rate is the number of births per year per 1000 people in the country, and a country's death rate is the number of deaths per year per 1000 people. Immigration refers to the number of people who move into a country each year, and emigration refers to the number of people who move out of the country each year. A country's population growth is determined by these four variables. Table 1 gives birth, death, immigration and emigration rates in four countries and lines 1−4 in Figure 1 model in the population for the four countries shown over time.
Birth Death Immigration Emigration
East Zealand 20 x 1000 1000
West Zealand 21 21 12100 y
South Zealand 36 24 z 500
North Zealand 13 13 82000 9600

what is the approximate value of y