2. Inventory at the end of March+purchase in the second quarter =400+880= 1280.
The sales cost in April, May and June is1280-420 (inventory at the end of June) =860.
The sales revenue in the first quarter is 6 million, and the sales revenue in the second quarter is 300+500+x = y.
The sales cost in the second quarter can be calculated according to the proportion of the previous quarter!
The average in the first quarter is 5 10/3= 170, and the average sales in the first quarter is 600/3=200.
That is, the unit sales cost per 200W is 170W, and the unit sales cost is 170/200=0.85.
We can calculate the cost in April: 300*0.85=255.
May cost: 500*0.85=425
The cost in June is: 860-255-425= 180.
I don't know if this answer is satisfactory!