Thelma counted the number of apples on each of the apple trees in her backyard. She found $34$ apples on her Cortland apple tree, $29$ apples on her Red Delicious apple tree, $39$ apples on her Empire apple tree, and $34$ apples on her Fuji apple tree.
**Find the mean absolute deviation (MAD) of the data set.**
[[☃ numeric-input 1]] apples