Gladstone Company tracks the number of units purchased and sold throughout each accounting period but applies its inventory costing method at the end of each period, as if it uses a periodic inventory system. Assume its accounting records provided the following information at the end of the annual accounting period, December $31.$

$\backslash$table$[[$Transactions$,$Units,,it$],[\backslash$table$[[$Beginning inventory, January $1],[$Transactions during the year:$]],1,600,$$$,40],[\backslash$table$[[$a$.$ Purchase, January $30],[$b$.$ Sale, March $14($ $$100$ each$)]],\backslash$table$[[3,650],[$