Consider the following sequential database: $\{$a$($bc$)$d$($e$)$f$,$b$($ac$)$d$($f$)$g$,($ab$)$c$($d$)$fb$,$e$($a$)$fcb$\}.$ Sup$-$ pose we are interested in finding frequent sequential patterns with a minimum support count of $2,$ but only those patterns where the items are all distinct $($no item repeats within the pattern$).$

$1.$ List all frequent length$-2$ sequential patterns that satisfy the distinct item constraint.

$2.$ Using the PrefixSpan algorithm, find all frequent length$-3$ sequential patterns that

start with item c and satisfy the distinct item constraint.

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