Build a Simple Business Margin Calculator for PC and Mobile

We are seeking a developer to create a simple percentage Margin Calculator application for our business. The application will function as the business equivalent of a pocket calculator, allowing users to enter cost figures, select a gross margin percentage and automatically calculate the required selling price. The ideal candidate will have experience in application development and be able to deliver a simple, reliable and user-friendly solution. The app should look, feel and work like a pocket calculator. Its purpose is to take a small number of cost-of-sale figures, total them, apply a selected gross margin percentage, and show the required selling price. This is a one-off fixed-price job. The application has one core purpose: to make margin-based pricing calculations simple, consistent and error-proof for staff preparing quotations. Users will enter several cost-of-sale figures, usually 5 to 20 lines, select a gross margin percentage from a menu, and the application will automatically calculate: 1. Total Cost of Sale 2. Gross Profit (£) 3. Gross Margin (%) 4. Required Selling Price (£) The application must be simple, reliable and easy to use on both PC and mobile phone devices. It should function like the calculator found on a Windows computer: the user clicks the icon, the calculator opens, the user completes the calculation, copies manually by handwriting the result into their next record, and closes it. No saving is required for Version 1.0. Please explain: * Your recommended technical approach. * Whether you would build it as a native, web or hybrid application. * Estimated timescale. * Fixed project price. * Ongoing support and maintenance options. * Ownership of source code and intellectual property. The application should work on Windows PC, laptop and mobile phone, giving a simple desk or pocket calculator style experience. Low cost of ownership, simplicity, ease of maintenance and reliability are important. It is not: * A CRM system * An accounting package * A project management system * A workflow system * A management information system * A sales pipeline system * A business intelligence platform * An estimating package * An ERP system No integration with other applications is required. Please begin your proposal with the words "Margin Calculator" so we know you have read the brief.