Complete the recursive function prefixes$-$from as described above, so that the wrapper function prefixes produces a list of a string's prefixes, in increasing order by size.;; prefixes$-$from: Nat Str $->($listof Str$)$

$($define $($prefixes$-$from k str$)$

$...)$

;; prefixes: Str $->($listof Str$)$

$($define $($prefixes str$)($prefixes$-$from $0$ str$))$