Alright I'm a bit stuck here, because I keep going in circles because I feel like I don't have enough information to complete the problem. I know there's got to be a trick somewhere! The question is:

A million years ago, an alien species built a vertical tower on a horizontal plane. When they returned they discovered that the ground had tilted so that measurements of 3 points on the ground gave coordinates of (0, 0, 0), (3, 2, 0), and (0, 3, 1). By what angle does the tower now deviate from the vertical?

Alright, so I drew myself a picture, got the normal for the new plane (it's (2,3,9)) but now I'm stuck. If I could have the normal for the original plane, I could just stick it into the geometric formula for dot products and get the angle between the two...

What am I missing here?!