Question 446414
A-
There is only one way to include the eldest
There is only one way to include the youngest.
That leaves 8 others to choose from for three positions.

1*1*8*7*6
B-
This one I am not sure of.
How do you know if the eldest is there?
if the eldest isn't there
10*9*8*7*6

if the eldest is there
we leave out the youngest so there are only 8 ways left
1*8*7*6*5