Magento 2 Knockout JS – Bind Data from AJAX Response

I want to bind image source to following div.

<div class="head_label"><img class="bank_photo" data-bind="attr:{src: bankImage}"></div>

Following is my ajax call and their is my variable which I want to bind to image src.

define(
[
    'jquery',
    'ko',
    'Magento_Checkout/js/view/payment/default',
    'Magento_Payment/js/view/payment/cc-form',     
    'Magento_Payment/js/model/credit-card-validation/validator',
    'mage/validation'           
],
function ($, ko, Component) {
    'use strict';

    var bankImage = '';

    return Component.extend({
        defaults: {
            template: 'Nitesh_Payment/payment/form',
            transactionResult: ''
        },
        ajaxCall: function(){
                $('#input-cc-number').blur(function(){
                    var cc = $(this).val();
                    var cc_length = cc.length;
                    if(cc_length>=6){
                        var data= {cc:cc}
                        $.ajax({
                            dataType: 'json',
                            url: url,
                            data: data,
                            type: 'post',
                            success: function(result)
                            {
                                var myObj = result;
                                this.bankImage = myObj.image;
                            },
                            error: function(){
                                alert("You Failed!");
                            }
                        });

                    }

                }); 
        },  

    });
}
);

Also I am unable to access bankImage variable inside Ajax call.
Please tell me how to access that variable in ajax function.