Simple Iphone/Android app - Quick turnaround, great design, potential future work

I require a simple app developing for IOS and Android using phone gap or equivalent. Here is a very brief outline of what is required.

App square icon
4 in app screens which will makes use of logo and some graphics
5 screen shots (For the App store description page, can use a mixture of in-app graphics and small banners)
Logo
Some simple equations which allow a user to type some information in and then work out the answers based on this information.

From this outline can you please give a rough estimation of cost? If it is something we can both work with I will be able to provide a NDA which will be followed by a full brief.
I would prefer to have someone work on the entire project rather than splitting it in to two. However I am interested in quotes for just design or build. I am very particular about design and therefore it is important you can show examples of previous work which has great design.

I am looking to start as soon as possible. Please be aware I have set a price which includes both design and build however please quote for one or the other if you can't do both.
Additionally please be aware that I like to stick to tight deadlines. We develop many apps, if the work is good there will be potential future work on the table.

Best Regards,

Edward