Harry has 3 sisters and 5 brothers. His sister Harriet has S sisters and B brothers. What is the product of S and B?
First, in Harry's point of view: 3 sisters and 5 brothers
And, in Harriet's point of view: 2 sisters, (3-1), 6 brothers, (5+1)
So, the product of S and B is, S∗B=6∗2=12.