find the expected return for investing in buildings in a metro area where the following three buildings are for sale:

The cost of the building is $4 million, the total rents are $500,000 and the total expenses are $300,000.

The cost of the building is $90 million, the total rents are $35 million and the total expenses are $24 million.

The cost of the building is $21 million, the total rents are $6 million and the total expenses are $3 million.