I don’t have the book in front of me but,
1,000 trip
Normal cruise .77 = 422 kts TAS on 1200 ibs per hour
Long Range .73 = 408 kts TAS on 800 ibs per hour
Trip time Normal cruise 2h 21 min
Long range 2h 27 min
Trip Fuel Normal cruise 2,832 ibs
Long Range 1,960 ibs
To save 6 minuets you have to burn 872 more ibs of fuel
Devide that by 6.75 ibs per gallon and you get 129 gallons
Multiply that my $6 per gallon and you get $775 to save 6 minuets, like I said it is not worth so much money to save so little time.