Can I please get help with this question?

QUESTION:

On March 1, Ben, a property owner, and Carl, a licensed contractor, executed a written agreement containing the following provisions: 1. Carl agrees to construct a residence using solar panels and related electrical equipment manufactured by Sun Company ("Sun") and to complete construction before Thanksgiving. 2. Ben agrees to pay Carl $200,000 upon completion of construction. 3. Ben and Carl agree that this written agreement contains the full statement of their agreement. 4. Ben and Carl agree that this written agreement may not be modified except upon written consent of both of them. Prior to execution of the written agreement, Ben told Carl that Carl had to use Sun solar panels and related electrical equipment because Sun was owned by Ben's brother, and that Carl had to complete construction prior to Thanksgiving. Carl assured Ben that he would comply. In August, Ben began to doubt whether Carl would complete construction prior to Thanksgiving; Ben offered Carl a $25,000 bonus if Carl would assure completion, and Carl accepted and gave his assurance. To complete construction prior to Thanksgiving, Carl had to use solar panels and related electrical equipment of equal grade manufactured by one of Sun's competitors because Sun was temporarily out of stock. Carl completed construction prior to Thanksgiving. Ben, however, has refused to pay Carl anything. What are Carl's rights and remedies against Ben? Discuss.Your answer should demonstrate your ability to analyze the facts in the question, to tell the difference between material facts and immaterial facts, and to discern the points of law and fact upon which the case turns. Your answer should show that you know and understand the pertinent principles and theories of law, their qualifications and limitations, and their relationships to each other. Your answer should evidence your ability to apply the law to the given facts and to reason in a logical, lawyer-like manner from the premises you adopt to a sound conclusion. Do not merely show that you remember legal principles. Instead, try to demonstrate your proficiency in using and applying them. If your answer contains only a statement of your conclusions, you will receive little credit. State fully the reasons that support your conclusions, and discuss all points thoroughly. Your answer should be complete, but you should not volunteer information or discuss legal doctrines that are not pertinent to the solution of the problem. Unless a question expressly asks you to use California law, you should answer according to legal theories and principles of general application