When a piece of wood is distorted by a karate chop, the top of the board is compressed while the bottom is stretched as shown. Therefore, you must first consider the change in length of the bottom of the board where the break begins. Chantal is a black belt in karate and she breaks a 30.0-cm piece of wood with a force of 70.0 N, changing it in length by 4.0 x 10-4 cm. What is the cross-sectional area of the piece of wood?