Assume for purposes of all parts of this question only that on Tuesday, October 19, 2021, Sean signs PSR's written proposal form and mails it to Kim at the address noted on the form. Kim receives the signed form (in an envelope postmarked October 19, 2021) in the mail on Friday, October 22, 2021. On November 1, 2021, Sean personally hands Kim a check payable to PSR for $1,800, the first month's payment for the snow removal service. At this point on November 1, 2021:

a. Do Sean and PSR have a bilateral or a unilateral contract? (Briefly explain the reason for your choice) (2.5 Points)

b. Do Sean and PSR have an executed or an executory contract? (Briefly explain the reason for your choice). (2.5 Points)

c. The 2021-2022 Winter Season proves to be an extremely snowy one. (I hope not!) On Wednesday, January 26, 2022, Kim visits with Sean and tells him that given the extreme amount of snow that has fallen, the price of gas, and the expensive repairs PSR had to make to the plow it uses for snow plowing at the Quakertown, PSR is 7 going to have to charge Sean $2,100 per month for February and March for snow removal at the Quakertown. Kim says that even with the increase, PSR will only be breaking even. Sean, who has been extremely pleased with PSR's snow clearing service, agrees to pay PSR the extra $600, provided that he can pay it to PSR in April (when Sean is expecting his income tax refund). Kim agrees to Sean's payment terms, and PSR continues snow plowing and snow blowing at the Quakertown during February and March 2022. Sean pays PSR $1,800 on each of February 1 and March 1, 2022. Sean receives his income tax refund on April 20, 2022. By June 1, 2022, however, Sean has not paid PSR the additional $600 agreed to in January. If PSR sues Sean for breach of contract, should the court order Sean to pay PSR $600? Why or why not? (3 Points)