1.21 A children's abacus has ten beads on each of the three rods (as shown in the figure). The beads on each rod are to be divided into two parts (no part can be empty). Now, we want the product of the three numbers of beads on the left side to equal the product of the three numbers of beads on the right side. How many ways are there to distribute the beads?
（Beijing, China High School Grade 1 Mathematics Competition, 1987）