please don't copy and paste. show me the work. thanks

A record of transactions for the month of May was as follows: Purchases Sales May 1 (balance) 400 @ $4.20 May 3 200 @ $7.00 4 1,300 $4.10 6 1,000 @ 7.00 8 800 @$4.30 12 900 @ 7.50 14 700 @ $4.40 (a) Assurning that perpetual inventory records are kept in dollars, determine the inventory using the average cost inethod. (b) Calculate the gross profit