Q1. THE FIRST ATTENDANCE QUESTION WAS:
What is derangement

A1. MY ANSWER TO THE FIRST ATTENDANCE QUESTION IS:
A derangement is a permutation of the elements of a set, such that no element appears in its original position



Q2. THE  SECOND ATTENDANCE QUESTION WAS:
Two examples of WtoS and StoW

A2. MY ANSWER TO THE  SECOND ATTENDANCE QUESTION IS:
StoW({1,2,3},3)
[1, 1, 1]
StoW({1,2,3,3},4)
[1, 1, 1, 0]
WtoS({1,1})
{1}
WtoS({1,1,0,0})
{2}