During the current year, a couple cashes in $10,000 of Series EE savings bonds to help pay the cost of their son's college education. Of this amount, $5,200 represents principal and $4,800 represents interest. They use $7,000 of the proceeds to pay for tuition and the rest to cover their son's room and board. The couple's modified AGI is $137,250. Which of the following statements is true?

A portion of the interest is taxable, and a portion of the interest is tax-free.

All of the interest is tax-free.

All of the interest is taxable.