Make a Market I

Let's say you have product $A$ in which you are quoting $4 \text{ @ } 5$ and product $B$ in which you are quoting $10 \text{ @ } 12$. $X \text{ @ } Y$ means that $X$ is our bid and $Y$ is our ask. We want to make a market on the product $A + B$. What is the bid-ask spread you will quote? Give the answer in the format of $Y^2 - X^2$