function money(workdays, hnetto, zus, costs) {
    workdays = workdays !== undefined ? workdays : 0;
    hnetto = hnetto !== undefined ? hnetto : 0;
    zus = zus !== undefined ? zus : 0;
    costs = costs !== undefined ? costs : 0;
    var mnetto = workdays * 8 * hnetto;
    var costs_netto = costs/1.23;
    var costs_vat = costs - costs_netto;
    var vat = mnetto*0.23;
    var brutto = mnetto+vat;
    var tohand = mnetto - zus - ((mnetto-costs_netto)*0.19);
    console.log('faktura brutto: ' + brutto + ', vat: ' + (vat - costs_vat) + ', earned: ' + tohand);
}