b$.$ Change reference counts based on the assignment $p=$ nullEdit or mark the diagram below to show the reference count for each block. Edit or mark the

copies of the diagram that follow to show how the successive assignment statements will cause

the reference counts to change and when blocks will be reclaimed. Each assignment after the first

should cause changes based on the state of the diagram after the previous statement.

a$.$ Change reference counts based on the assignment $r=s$

IR

b$.$ Change reference counts based on the assignment $p=$ null