For the data set 7, 10, 10, 14, 14, 17, the mean is 12. What is the mean absolute deviation?

The mean absolute deviation is 18.
The mean absolute deviation is 12.
The mean absolute deviation is 6.
The mean absolute deviation is 3. I NEED IT NOW!

The figure shows triangle def and line segment bc, which is parallel to ef: triangle def has a point b on side de and point c on side df. the line bc is parallel to the line ef. part a: is triangle def similar to triangle dbc? explain using what you know about triangle similarity. part b: which line segment on triangle dbc corresponds to line segment ef? explain your answer. part c: which angle on triangle dbc corresponds to angle f? explain your answer. asap