Can You Solve This Brainteaser?

"Here is Edward Bear, coming downstairs now, bump, bump, bump, on the back of his head, behind Christopher Robin." So begins the children's book Winnie-the-Pooh (1926).

Which letter in the word BEAR can be added to the word ANIMAL to form, when the letters are rearranged, the seven-letter first name of the wife of a president of the United States? What are that first lady's first and last names?

English author of Winnie-the-Pooh in 1922.

(The seven letters of that author's name can be rearranged

to form the first name of a first lady of the United States.)