12. A receiver tank is used to
a. hold the excess refrigerant during lighter loads
b. collect oil from the base of a riser
c. separate liquid from vapor refrigerant
d. all of the above
13. The flow rate per ton of refrigeration effect for R-502 having a saturated suction temperature of 20 ํF and liquid entering the metering device at 110 ํF is
a. 5.10 lbm/ton
b. 5.75 lbm/minute ton
c. 5.75 lbm/ton
d. 5.10 lbm/minute ton