He needs to keep his total time at 300 or below because 5 x 60 = <<5*60=300>>300
His total time spent in the other mazes is 200 because 4 x 50 = <<4*50=200>>200
His total time spent in the five mazes thus far is 245 because 200 + 45 = <<200+45=245>>245
He can spend 55 more minutes on this maze before his average go above 60 because 300 - 245 = <<300-245=55>>55
#### 55