What is the cost per hour to run a 5 hp fan at 277volt @ .14 per kwh

1 hp = 745.699872 watt

\Large 5\,hp \,\times\, \frac {0.746\,kw}{1\,hp}=3.728\,kw

Thus, in 1 hour, you'll burn 3.728 kw

3.728\,kwh\times \frac {0.14}{kwh}=0.522

Of course, this does assume that the 5 kw refers to actual power consumed and includes all losses (heat, etc). The 277 volts is irrelevant.