Erwick Construction Company contracted to build a house for Charles. The specifications called for the use of Karlene Pipe for all plumbing. Erwick, however, got a better price on Boynton Pipe and substituted the higher quality Boynton Pipe for Karlene Pipe. Upon inspection, Charles discovered the change, and he now refuses to make the final payment. The contract price was for $200,000, and the final payment is $20,000. Erwick now brings suit seeking the $20,000. Will Erwick succeed in its claim? What contract issues are involved?