$2-1$ Bob Johnson decided to purchase a new bome. After looking at tracts of new homes, he decided that a custom$-$built home was preferable. He hired an architect to prepare the drawings. In due time, the architect completed the drawings and submitted them. Bob liked the plans; he was less pleased that he had to pay the architect a fee of $$4000$ to design the house. Bob asked a building contractor to provide a bid to construct the home on a lot Bob already owned. While the contractor was working to assemble the bid, Bob came across a book of standard house plans. In the book was a home that he and his wife liked better than the one designed for them by the architect. Bob paid $$75$ and obtained a complete set of plans for this other house. Bob then asked the contractor to provide a bid to construct this "stock plan" home. In this way Bob felt he could compare the cosis and make a decision. The building contractor submitted the following bids:

Custom$-$designed home

$$128,000$

Stock$-$plan home

$128,500$

Bob was willing to pay the extra $$500$ for it$.$ Bob's wife, however, felt they should go abead with the custom$-$designed home. for, as she put it$,"$We can't afford to throw away a set of plans that cost $$4000."$ Bob agreed, but he disliked the thought of building a home that is less desirable than the stock plan home. Then he asked your advice, Which house would you advise him to build? Explain.