var hostName = 'http://www.multilevelsystem.com';

function updateFinalPrice(duration, unit) {   
    var finalPrice = document.getElementById('finalPrice');
    if (isNaN(duration)) {
        var price=0;
        switch (duration) {
            case 'promo1':
                price=unit*5;
                break;
            case 'promo2':
                price=unit*9;
                break;                
        }
        finalPrice.innerHTML=price;
    } else {
        finalPrice.innerHTML = duration*unit;
    }
}