Calculer somme valeur tableau javascript

var prestation = [
   ["banniere", 100, 0],
   ["affiche", 40,30 ],
   ["illustration", 50, 0],
  
];

var mont_presta = new Array();

for (var i = 0; i < prestation.length; i++) {

 mont_presta[i]= prestation[i][1] + prestation[i][2]  +"<br>";
 	
 document.write(  mont_presta[i] +"<br>" ); 
		}
		
		
var total = 0;

for(var j = 0 ; j < mont_presta.length; j++){
    
    total = total + mont_presta[j];
	
	}
	
	document.write( total );

var prestation = [
   ["banniere", 100, 0],
   ["affiche", 40,30 ],
   ["illustration", 50, 0]
];

var mont_presta = new Array();

for (var i = 0; i < prestation.length; i++) {
  mont_presta[i]= parseFloat(prestation[i][1]) + parseFloat(prestation[i][2]) ;	
  document.write(  mont_presta[i] +"<br>" ); 
}
		
		
var total = 0;

for(var j = 0 ; j < mont_presta.length; j++){ 
  total += parseFloat(mont_presta[j]);
}

document.write( "Total = " + total );

var prestation = [
   ["banniere", 100, 0],
   ["affiche", 40,30 ],
   ["illustration", 50, 0]
];

var total = 0;
for (var i = 0; i < prestation.length; i++) {
  var mont_presta = parseFloat(prestation[i][1]) + parseFloat(prestation[i][2]);
  document.write(  mont_presta +"<br>" ); 
  total += parseFloat(mont_presta);
}
document.write( "Total = " + total );