What is the dogs average acceleration from 0 to 12 seconds

Aheavy boy and a lightweight girl are balanced on a massless seesaw. the boy moves backward, increasing his distance from the pivot point. what happens to the seesaw? it is impossible to predict without knowing additional information. the side the boy is sitting on will tilt downward. the side the girl is sitting on will tilt downward. nothing; the seesaw will remain balanced.