Take a look at the photo below. The tenants at this apartment house complained to the landlord that they were seeing suspicious characters in the yard and on the walkways between the apartments. They asked the landlord to install a security gate at the entrance to the yard. The landlord gave the tenants what they asked for. He had a contractor install a security gate at the entrance to the yard, but for some reason, the tenants are still not satisfied. Can you figure out why?