In 2018, Alpha Company had $48,000,000 in Sales/Revenues, $15,500,000 in Costs of Goods Sold (COGS), $3,600,000 in Sales, General, and Administrative (SG&A) expenses, $1,200,000 in Depreciation expenses, $550,000 in interest payment, and $4,215,000 in taxes. The firm also paid $1,900,000 in dividends to shareholders that year. Given the facts above, what was the average tax rate of the firm in 2018?