After installation of a field-piped r-410a split heat pump, the unit should first be:

After installation of a field-piped R-410A split heat pump, the unit should first be:pressurized with nitrogen then leak checked.Heat Pumps that have been retrofitted from R-22 to R-407C should be leak checked with:pressurized nitrogen.The EPA regulations require that leaking commercial or industrial process refrigeration equipment must be repaired when the leak rate exceeds of the charge per year.35%

Ithink the answer is c.  hope this is right and