----------------  SOLUTION  -------------------

solution cost   : 495.848
number of trips : 6

trip 1, 5 customers, sequence : 9 7 5 6 8 
   weight    : 3900
   volume    : 5
   trip cost : 88.6468

trip 2, 4 customers, sequence : 2 1 3 4 
   weight    : 4000
   volume    : 4
   trip cost : 123.434

trip 3, 4 customers, sequence : 14 17 20 18 
   weight    : 4000
   volume    : 4
   trip cost : 74.5286

trip 4, 2 customers, sequence : 21 19 
   weight    : 3200
   volume    : 2
   trip cost : 76.2762

trip 5, 4 customers, sequence : 15 12 10 11 
   weight    : 4000
   volume    : 4
   trip cost : 92.6603

trip 6, 2 customers, sequence : 13 16 
   weight    : 3400
   volume    : 2
   trip cost : 40.3023