Develop Custom Admin Plugin For WP to Admin Payments API's

We need experienced php, WordPress, Payments API developers to take a custom PHP app and convert into a Plugin for the Admin user. Functions needed in this custom plugin are: 1. Admin can add and edit current payment processors API and other related processor Info - We need page(s) created for this task (We have example pages for reference) 2. Admin can select which processor (Payment API) the USER is to use. Again we need custom built "options" page to do so. where all the pertinent Data fields information will be given to you. 3. Admin can add and edit rates/ fees on which the processor charges. - We need a custom page built for this task. You can view the project in details here -> [login to view URL]