Mary has Taxable Income for the current year of $325,000, of which $216,000 is spent on goods and services that are subject to HST at a rate of 13 percent. Her sister, Joan, is a part-time student living in the same province and has Taxable Income of $19,000. During the current year, as a result of using some of her savings, she spends $22,400 on goods and services that are all subject to HST. Determine the effective HST rate as a percentage of the income of the two sisters.