Lumen method: PE Power General Applications practice question

An open office is 50 ft long and 30 ft wide with a 10 ft ceiling. The design calls for a maintained average illuminance of 50 fc on a work plane 2.5 ft above the floor. The designer uses recessed 2 ft × 4 ft LED troffers rated 4,400 lumens each, with a light loss factor of 0.85. For this room's reflectances, the manufacturer's coefficient of utilization (CU) table gives:

Room cavity ratio	1	2	3
CU	0.80	0.73	0.66

Using the lumen method with the room cavity ratio $RCR = 5h(L + W)/(L W)$, the minimum number of luminaires is most nearly: