# Somone can help me to solve this question about the AC-3 algorithm

i was watching this video: https://www.youtube.com/watch?v=4cCS8rrYT14 and I tried to solve this question:

"Given the variables A, B, C and D, with domain {1, 2, 3, 4} in each of them and restrictions A> B, B = C and D ≠ A, use the AC algorithm."

But the teacher told me that my answer was wrong! He gave me a tip, the tip is: Domain D will not be changed! Below, I will leave my answer step by step, if someone can help me find the error, I appreciate it!

To solve this exercise, it is first necessary to organize the data in order to separate what is the domain, agenda and arc.

Soon after, we will analyze the first item on the agenda “A> B” with domain A, in order to eliminate unnecessary elements from the domain.

Analyze domain B with the agenda item “B <A”

Analyze domain B with the agenda item “B = C” and add the constraint “A> B”

Analyze domain D with the agenda item “D ≠ A” and add the constraint “B <A”

Analyze domain A with the agenda item “A ≠ D”

Analyze domain A with the agenda item “A> B”

Analyze domain B with the agenda item “B = C”

Analyze domain B with the agenda item “B <A”

Result