Answer:
There were three main characters in this story.
Della Dillingham Young (dynamic)
James Dillingham Young (dynamic/ static)
Madame Sofronie (flat)
Explanation:
Della was a dynamic character throughout the story because she was always up for the help, support, care and sacrifice. She can handle and change according to the situation. She sold her hairs to buy gift to her husband.
James was a static character in start because change was not his thing but when he had no money for gift, he decided to sell his precious thing just make his wife happy by giving her gift so it was also his dynamic side. So, James was both dynamic and static.
Madame Sofronie was a flat business woman who had no concern what Della is going through or what hairs meant to her. She didn't even look properly and told Della the price. So, madame Sofronie was a flat, emotionless, harsh business woman.