Table:
text: List of Nashville Sounds seasons
Season-by-season records
Season-by-season records
Year_ Record_a_ Win_ League_b_ Division_c_ GB_d_ Post_season_record_e_ Post_season_win_ MLB_affiliate_f_
2006 # 76–68 .528 5th (tie) 1st (tie) — 2–3 .400 Milwaukee Brewers
2007 # 89–55 .618 1st 1st — 1–3 .250 Milwaukee Brewers
2008 59–81 .421 16th 4th 23 — — Milwaukee Brewers
2009 75–69 .521 5th 2nd 2 — — Milwaukee Brewers
2010 77–67 .535 5th 4th 5 — — Milwaukee Brewers
2011 71–73 .493 6th (tie) 3rd 9 — — Milwaukee Brewers
2012 67–77 .465 12th 2nd 16 — — Milwaukee Brewers
2013 57–87 .396 16th 4th 13 — — Milwaukee Brewers

Question: What is the average win percentage of a season with a GB of 5 for List of Nashville Sounds seasons?