Mary and Jo enter a contract in which Jo agrees to buy Mary's small consignment business for $300,000.

Mary and Jo enter a contract in which Jo agrees to buy Mary's small consignment business for $300,000.00. Jo goes home and realizes the stock market is reducing his financial position and perhaps this is not a good time to by another business. Jo has lunch with Peter and tells him the situation. Peter says he would love to buy Mary's business. 

Can Jo assign his right to buy Mary's business to Peter? Why or why not