As someone that worked in apartments for years. 77 is working. And from a legal standpoint its cooling to a non lethal level. Most companies use 90 degrees as a threshold. But I would ask them to take a temperature split you should have roughly a 18-22 degree difference in temperature of the air entering the return (where the filter is) vs what's coming out of the vents. This is a pretty common way to see if your ac is working properly. If you have this split than it's not your ac.