set ORIG;   # origins (steel mills)
set DEST;   # destinations (factories)
set PROD;   # products
set TRUCK;  # trucks
param pallet_w;                 # weight of each pallet.
param rate {ORIG,PROD} > 0;     # tons per hour at origins
param avail {ORIG} >= 0;        # hours available at origins
param demand {DEST,PROD} >= 0;  # tons required at destinations
param capacity {TRUCK} >= 0;    # truck's capacity in num. of pallets.
param crew {TRUCK} >= 0;        # number of trucks available
param make_cost {ORIG,PROD} >= 0;        # manufacturing cost/ton
param truck_cost {ORIG,DEST,TRUCK} >= 0;  # shipping cost/ton
param fix_cost {ORIG, PROD} >= 0;              # fixed costs
var Make {ORIG,PROD} >= 0;                  # tons produced at origins
var Prod {ORIG,PROD} binary;                # =1 produced, =0, not produced
var Pallets{ORIG,DEST,PROD} integer, >= 0;  # pallets shipped
var Trucks {ORIG,DEST, TRUCK} integer, >=0; # num. of trucks used
#minimize Total_Cost: sum{i in ORIG, j in DEST, l in TRUCK} Trucks[i,j,l];
minimize Total_Cost:
  sum {i in ORIG, p in PROD}             make_cost[i,p] * Make[i,p] +
  sum {i in ORIG, j in DEST, l in TRUCK} truck_cost[i,j,l] * Trucks[i,j,l] +
  sum {i in ORIG, p in PROD}             fix_cost[i,p] * Prod[i,p];


这道题目怎么做啊？如果火车的数量最少是10辆给条路线。