FIFO and WAC for inventory valuation

Appleby buys and sells inventory during the month of August as follows: Opening inventory 100 units $2.52/unit 4 August Sales 20 units 8 August Purchases 140 units $2.56/unit 10 August Sales 90 units 18 August Purchases 200 units $2.78/unit 20 August Sales 180 units The periodic weighted average for the month is calculated as follows: Total value of inventory (opening inventory plus purchase costs during the month) divided by total units (opening inventory plus purchase costs during the month). Which of the following statements is true? A Closing inventory is $19.50 higher when using the FIFO method instead of the periodic weighted average. B Closing inventory is $19.50 lower when using the FIFO method instead of the periodic weighted average. C Closing inventory is $17.50 higher when using the FIFO method instead of the periodic weighted average. D Closing inventory is $17.50 lower when using the FIFO method instead of the periodic weighted average. Answer is A) > Please help me find closing inventory valuation. According to FIFO method, I'm getting correct valuation of $417 but I have tried several times according to WAC method, I am not getting any answer similar to the options. Using WAC, my C.I value is 402.3 and 417- 402.3 = 14.7 difference which has no options.