Question $3$: $(20$ points for each case$)$

Write a predicate replacelast$/4$ that substitutes the first argument $x$ with the second argument $Y$ for the last element, an occurrence of $x$ in a list of elements. If the list is empty the result is the empty list. If $x$ is not in the list, then the result is the list itself.

hint: the last occurrent is represented by when the tail is empty : $[\frac{?}{xI}[]]$

Three cases

The list is empty, then the result is empty

$x$ matches the head, insert $Y$ in the new list and replace $x$ with $Y.$

$x$ does not match the head and the tail is the empty list head, replace $x$ with $Y$ in the tail

$?-$ replacelast$($a$,$z$,[$a$,$b$,$c$,$a$,$r$,$a$,$z$],$R$).$

$R=[a,b,c,a,r,a,z].$

$?-$ replacelast$($a$,$z$,[$a$,$b$,$c$,$a$,$r$,$a$,$y$],$R$).$

$R=[a,b,c,a,r,a,y].$

$?-$ replacelast $(1,6,[5,0,1,1,1,5,1],R).$

$R=[5,0,1,1,1,5,6].$

$?-$ replacelast$($a$,$z$,[$a$,$b$,$c$,$a$,$r$,$a$],$ R$).$

$R=[a,b,c,a,r,z].$