Answer:
Cost of goods available for sale is $ 3,750
Ending inventory is $2,600
Sales is $1,500
cost of goods sold is $1,150
gross profit is $ 350
Explanation:
FIFO Method is an Inventory System that Sells First the Oldest Inventory.
A periodic inventory system calculates the Cost of Inventory with each sale made rather than after a period ( Periodic)
Cost of goods available for sale
Cost of goods available for sale  = Opening Stock + Purchases
                            = (50× $10) + (250× $13)
                            = $ 3,750
Ending inventory
July 31 : 200× $13 = $2,600
Sales
July 25 : 100× $15 = $1,500
cost of goods sold
July 25 : 50× $10 = $500
       50× $13 = $650
Total           = $1,150
gross profit
Gross Profit = Sales - cost of goods sold
          = $1,500 - $1,150
          = $ 350