We are given that Bank A charges ordinary interest for a loan of $11000 at a rate of 9% for a period of 90 days, we can calculate the total interest using the formula for ordinary interest, this is:

Replacing that we get:

Solving we get:

Now, bank B charges exact interest, the formula is:

Replacing we get:

solving the operation:

Therefore, she will pay less interest to Bank B. Bank B offers a better deal.