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

solution cost   : 278.726
number of trips : 3

trip 1, 4 customers, sequence : 11 2 9 12 
   weight    : 89
   volume    : 4
   trip cost : 68.0366

trip 2, 6 customers, sequence : 14 13 4 15 10 5 
   weight    : 89
   volume    : 6
   trip cost : 114.563

trip 3, 5 customers, sequence : 1 3 8 7 6 
   weight    : 80
   volume    : 5
   trip cost : 96.1267