Average Commission

In B5:10 through E5:10 I have quarterly sales totals for six salespeople. Cells F5:10 have their sales totals for all four quarters. G5:10 has the commission earned over the four quarters based on the totals in Column F. This uses an IF function, as the commission is 5% if below $8000 and 10% if above that. Row 11 has the totals of Rows 5:10. In Column H, I need to find, as a percentage, the average commission for the year. Nothing I can think of works. I tried simply averaging B5:E5 and filling down, but I converting this into a percentage is proving frustrating. Where am I going wrong?