For the traversal log:

$$

$\{$X$,$ Y$,$ Z$,$ W$,$ Z$,$ Y$,$ A$,$ B$,$ C$,$ D$,$ C$,$ B$,$ A$,$ Y$,$ E$,$ F$,$ G$,$ H$,$ I, H$,$ G$,$ F$,$ E$,$ Y$,$ X$,$ Y$,$ A$,$ B$,$ M$,$ N$,$ O$\}$

$$

a$)$ Find the maximal forward references.

b$)$ Find large reference sequences if the threshold value is $0\mathrm{.}4($or $40\%).$

c$)$ Find maximal reference sequences $($MRS$).$