#primo stadio
var x1 >=-1 , <=1; 
var x2 >=0; var x3 >=0; var x4 >=0;
#secondo stadio
var abs1; var abs2;

param penalty := 0.2;

#scenari: probabilità
param prS1 := 0.7;
param prS2 := 0.3;

maximize z: x2-x1 -( 
		prS1 * penalty * abs1 
	  + prS2 * penalty * abs2 );
s.t. v1: x1 + x2 + x3 = 2;
s.t. abs1lin1: abs1 >=   2 - ( 1 * x1 + 3/4 * x2 + x4);
s.t. abs1lin2: abs1 >= - 2 + ( 1 * x1 + 3/4 * x2 + x4);
s.t. abs2lin1: abs2 >=   2 - (-3 * x1 + 9/4 * x2 + x4);
s.t. abs2lin2: abs2 >= - 2 + (-3 * x1 + 9/4 * x2 + x4);