An airport can either install escalators or elevators. Escalators can transport 20 people every minute whereas elevators can transport 8 people every minute. Escalators take up 5 units of space while elevators take 2 units of space. The airport needs to have enough capacity to transport at least 400 people every minute. Additionally, there must be at least three times more escalators than elevators and at least 2 elevators must be used. How many of each type should the airport install to minimize the total units of space taken?