I would like to know how the sales was calculated for step $4$

Required Information

$[$The following information applies to the questions displayed below.$]$

Warnerwoods Company uses a perpetual Inventory system. It entered Into the following purchases and sales transactions

for March.

Compute gross profit earned by the company for each of the four costing methods. For specific identlfication, units sold include $80$

units from beginning Inventory, $340$ units from the March $5$ purchase, $40$ units from the March $18$ purchase, and $120$ units from the

March $25$ purchase.

Note: Round welghted average cost per unit to $2$ decimal places.