Corbin, owner of Cascade Construction, tells Bethany he has no contractors' license but he will remodel her kitchen for half the cost of the highest licensed bidder. Bethnay agrees, shows him the highest bid ($40,000) and Corbin agrees in writing (both sign) to do the work for $20,000. His materials cost $8,000 and $12,000 is for his labor. When he finishes, she refuses to pay him anything. Can he sue her and is it a strong case? Briefly explain.