function conc(x, y_theoretical, y_measured) {
var self = this;
self.x = ko.observable(x);
self.y_t = ko.observable(y_theoretical);
self.y_m = ko.observable(y_measured);

function ConcentrationViewModel() {

var self = this;

self.concentrations = ko.observableArray([
    new conc(2, 9, 8),
    new conc(6, 10, 11),
    new conc(8, 12, 13),
    new conc(10, 14, 15),
    new conc(14, 16, 17),
    new conc(19, 18, 19)
]);

self.a = ko.computed(function() {
    var res = self.concentrations[0].x + self.concentrations[1].x;
    return res;
},this);

self.b = ko.computed(function() {
    return 15;
},this);

debugger;
 ko.applyBindings(new ConcentrationViewModel());
 debugger;

var value = self.myObservableProperty();

self.myObservableProperty(newValue);

self.a = ko.computed(function(){
    var allConcentrations = self.concentrations();
    return allConcentrations[0].x() + allConcentrations[1].x();
});