Subject: mathqa
Question: a block of wood has dimensions 10 cm x 10 cm x 40 cm . the block is painted red and then cut evenly at the 20 cm mark , parallel to the sides , to form two rectangular solids of equal volume . what percentage of the surface area of each of the new solids is not painted red ?
Option: 
A: 5 %
B: 25 %
C: 15 %
D: 10 %
Answer: D