Duck calls

In week 3’s first assignment, you learned about all of Bill’s legal woes. Well, Bill is back again. And it again concerns his side business of building duck calls.
Shortly after his first visit with you, Bill went to a Wild Game Dinner. At the event, Bill met Joseph, who is the cousin of one of Bill’s neighbors. Joseph has a sports and hunting store in Clarksville, TN. Bill told Joseph about his duck calls. Joseph said that he would be interested in selling them in his store on a trial basis. To encourage him to do the trial, Bill told Joseph that he would give him a discounted price for his first order. 
The next week, Joseph sent Bill his store’s standard purchase order form, which included pre-written terms, such as an arbitration clause and a warranty of merchantability. Joseph requested to purchase 50 units at the “discounted” price that Bill spoke of at the event. Joseph requests to pay for the units in 90 days. 
Bill was excited. He quickly sent a written confirmation to Bill. However, in the confirmation, Bill again made some typographical errors. First, Bill wrote the wrong price. Second, Bill wrote the wrong number of units.  In pertinent part, Bill’s confirmation stated:
“Thanks for agreeing to try selling my duck calls in your store. As I mentioned, I will give you a discounted price. I normally sell my handcrafted wooden duck calls to retailers for $43.00 with a suggested retail price of $59.99. Since you are trying them out, I will sell you 500 for $3.500. I will send you the units as soon as I have them ready. I have no problem with payment in 90 days from now.”
Joseph reviewed the written confirmation a few days later. Joseph is initially upset about Bill increasing the units from 50 to 500; however, after seeing the discount he is getting, Joseph has no problem with the increased purchase order. He believes that, if they do not sell well, he can easily sell the duck calls for $12.99 and make a good profit. As such, Joseph does not say anything to Bill about the increased purchase order. Instead, Joseph tells Bill, “I agree to the terms you sent.” 
Bill sends Joseph 50 duck calls about a week after Joseph’s confirmation. Joseph likes the duck calls and thinks they are good quality. He places them on sale for $29.99 and sells the first 50 units in two weeks. As such, Joseph is anxious to get the next batch. He sends Bill an email, stating in pertinent part: “The ducks calls are a big hit! I’ve sold out! Send me the remaining units as quick as you can. Do you have any idea when you will send more units?”
Bill is confused by Joseph’s email. Bill reviews the prior correspondence and sees his two errors. He calls Joseph and tells Joseph about the errors. Joseph thinks Bill is now regretting their deal since the duck calls sold so fast. He believes that Bill wants to sell his duck calls at a higher price. Joseph tells Bill that he cannot back out of their deal now because they have a contract.
Bill has come to you for help. Please give Bill some guidance on this mess he has gotten himself into. (20 points)

No other sources than what is provided.