1,200 Gallons.
Economic ordering quantity (EOQ) is the most cost efficient amount to order that minimizes both carrying and order costs. The formula is
[tex]\sqrt{(2*units *ordering costs)/holding costs \\\\[/tex]
[tex]\sqrt{405,000*32 / 9\\\[/tex]
[tex]\sqrt{1,440,000[/tex]
1,200 gallons