#variabili: xoa, xob, xoc, xab, xat, xbc, xbt, xca, xct
var xoa binary;
var xob binary;
var xoc binary;
var xab binary;
var xat binary;
var xbc binary;
var xbt binary;
var xca binary;
var xct binary;

minimize costo: 
	10*xoa + 10*xob + 5*xoc + 
	10*xab + 7*xat + 
	10*xbc + 10*xbt + 
	7*xca + 10*xct;

s.t. balance_o: xoa + xob + xoc = 1;
s.t. balance_t: xat + xbt + xct = 1;
s.t. balance_c: xoc + xbc - (xca + xct) = 0;
s.t. balance_b: xob + xab - (xbc + xbt) = 0;
s.t. balance_a: xoa + xca - (xab + xat) = 0;