Cartoon / illustration for small business marketing campaign

I need a single-frame cartoon drawn up of three birds sitting in a grape vine, having a conversation. The style can be a simple line drawing and be in B+W, but I'd need high-res jpeg or vector files supplied.
Exact details of the cartoon and conversation between the characters will be supplied to shortlisted proposals.
The winning bidder will also need to supply a quick concept sketch of their drawing for approval before working on and delivering the finished file.
I'd suggest the sketch would take half an hour, and the finished work and file deliverables would be a further two hours' work.
Please give a full cost estimate of the job in your proposal.
Any questions, just ask! Good luck.