You have agreed to paint your neighbor's house a lovely shade of chartreuse for $1500 and discover, much to your dismay, that the house has a second floor. Now you're faced with the prospect of buying a ladder or scaffolding (or a really long handled brush), not to mention the 15 more gallons of paint that will be needed to cover the additional portions of the house. You won't get another penny for what will surely be increased efforts since your neighbor transferred all their cost risk to you with a(n):