$(document).ready(function() {
    $("#givingForm select").change(function() {
        var total = 0;
        total += $("#givingForm select[name=school_supplies]").val() * 25;
        total += $("#givingForm select[name=math_tools]").val() * 50;
        total += $("#givingForm select[name=celebrations]").val() * 100;
        $("#givingForm input").val("$" + total.toString());
    });
});