Here's a similar question, Robert:

Q. What is the product of the x-intercept and y-intercept of 2x - 4y = 16?

A. The x-intercept is the value of x when y is zero, so 2x = 16, so x = 8.
The y-intercept is the value of y when x is zero, so -4y = 16, so y = -4.
The product of these intercepts is 8 times -4, which is -32.

Now you try your question, using the same idea.

Hope this helps,
Stephen La Rocque.