Units to be produced in February is calculated as -
Units to be produced in February = February sales + Ending inventory of February - Beginning inventory
February sales = 4,600 units
Ending inventory = 25 % * Sales of March = 25 % * 5,300 units = 1,325 units
Beginning inventory - 25 % * Sales of February = 25 % * 4,600 unit = 1,150 units
Units to be produced in February = 4,600 units + 1,325 units - 1,150 units
Units to be produced in February = 4,775 units