Periodic Inventory by Three Methods Dymac Appliances uses the periodic inventory system. Details regarding the inventory of appliances at January $1,$ purchases invoices during the next $12$ months, and the inventory count at December $31$ are summarized as follows: $[[$Purchases Invoices$],[[[$Model$],[$A$10]],[[$Inventory$,],[$January $1]],1$st$,2$nd$,3$rd$,[[$Inventory Count,$],[$December $31$