please someone who can give a step by step explanation for this problem. thank you

QUESTION 36 Echo Sound Company just began business and made the following four inventory purchases in June: June 1 June 10 June 15 June 25 150 units 200 units 200 units 150 units S 1,040 1,360 1,680 1.320 $5.600 image A physical count of merchandise inventory on June 30 reveals that there are 210 units on hand. The inventory method which results in the highest gross profit for June is a. the FIFO method. the LIFO method C the average cost method. d. not determinable 5 points D