At a national seashore, the number of swimmers per day who require lifeguard assistance averages 4.1, on any day when 7 or more swimmers are assisted, the lifeguards receive a $20 bonus for extra effort. Bob's base life-guarding pay is $12 per hour for each 8 hour day. Taking into account the extra-effort days that sometimes occur, what is Bob's average pay for an 8 hour day?