Banner and button design for an educational web site

We need you to design static banners for a non-profit educational web site. The precise themes and texts to include will be detailed to the winning provider. We expect to receive four different banner designs, each in sizes 468 x 60, 728 x 90 and 120 x 600 pixels. Each of the designs needs to be approved by us before accepting it as a finished result. The resulting banners should invoke at least one or several of the following themes: education, cooperation, trust, global connection, reliability. Each banner should include logo which will be supplied. If you wish to be considered, please supply some examples of your previous banner work. We need this to be done in 48 hours and will pay $50 max. Thanks for looking!