Please explain detail solution with Excel sheet, please.

1st pic: question

2nd question: Need to answer. please help me. Thank you so much!!

P2-3 Economic order quantity; tabular computation Chavez Chemical Inc. requires 20,000 gallons of material annu- ally; the cost of placing an order is $20; the annual carrying cost per gallon is $5. Required Determine the EOQ from potential order sizes of 300, 400, 500, 600, 700, and 800 gallons by constructing a table similar to the one appearing on page 71