set vessels;
set ports;
param cost{vessels};
param capacity{vessels};
param t{vessels,ports};
param available{ports};
param fcost{ports};
param demand >= 0;

var x{vessels,j in ports} >= 0;
var y{ports} binary >= 0;
var z{vessels} binary >= 0;
var k{vessels,ports} binary >=0;

minimize totcost: sum {i in vessels,j in ports} x[i,j] * t[i,j]+
				  sum {i in ports} y[i]*fcost[i]+
				  sum {i in vessels} z[i]*cost[i];

subject to port_Capacity{j in ports}:
		sum {i in vessels} x[i,j] <= available[j]*y[j];

subject to DEMAND: sum{i in vessels,j in ports} x[i,j] >= demand;

subject to FIXED_COST {i in vessels}:
        sum {j in ports} x[i,j] <= z[i]*capacity[i];

subject to maxVisits {i in vessels}:
  		sum {j in ports} k[i,j] <= 2;

subject to Amount {i in vessels, j in ports}:
		k[i,j]*999999999>=x[i,j];