Write SELECT queries to show the requested data for each of the items below:

I am using sqlzoo select from world tutorial to test this and want to know how to do these two

1. Show the population per square km (area) for countries in North America. Name the calculated field pop_per_sq_km (hint: use the alias keyword AS).
2. Show the gdp per capita (that is, per person) for countries in Africa. Name the calculated field gdp_per_capita (again use AS)

Just got #2 only need #1 now

2. SELECT name, gdp/population AS gdp_per_capita FROM world WHERE continent = "Africa"