The Wilson family decided to have a pool built in their backyard. Under the existing contract the pool was to be completed by June 1, just in time for summer. Just before work was to begin, the pool contractor met with the Wilsons and explained that due to a shortage of workers, the completion date could not be met. He said that for an extra $5,000, however, additional workers could be hired and the pool would be completed on time. The Wilsons told the contractor that they would pay the $5,000. On June 1, the pool was completed, and the contractor asked for the additional $5,000 payment.

a) Are the Wilsons legally obligated to pay?Why or why not?

b) Would it make a difference if, while digging the hole for the pool, the contractor unexpectedly hit solid rock and needed an additional $5,000 to use jackhammers or even dynamite to finish?

c)What if, in addition to completing the pool as originally designed, the contractor adds a waterfall. Would he be entitled to the extra $5,000 payment then?