Long description

The figure shows three trees, the first tree is labeled Hard disk which is starting with a square block connected to two blocks labeled a and b. Block a is connected to two blocks labeled c and d. Block c is connected to two blocks p and q. The block d is connected to a block labeled r. The second tree is labeled USB which is starting with a square block and is connected to three blocks labeled x, y, and z. The third tree is labeled Hard disk which is starting with a square block connected to two blocks labeled a and b. Block a is connected to two blocks labeled c and d. Block c is connected to two blocks p and q. The block d is connected to a block labeled r. The block b is connected to three blocks labeled x, y, and z.