For this proposal, you will bid on a particular project in writing, hoping to convince a potential client to let you conduct research for them. In this case, your bid is, of course, artificial: everyone is going to be working with the same site. However, you should imagine that you are writing directly to the client, competing to win their business. In a comprehensive proposal, you will demonstrate your expertise and explain why your team, in particular, is best suited to the task.
