JESS: How can I write this rule?

[Jeremic Zoran]

(deftemplate passed_concepts (slot ID (type INTEGER)))   (deftemplate concept (slot ID (type INTEGER)) (multislot prerequisite) (slot ordinalNumber (type INTEGER)) (slot minKnowledgeLevel (type INTEGER)))   there could be up to 23 passed_concepts in memory, and every concept could have 1, 2 or 3 prerequisites. I need to write rule that will find concept (fire rule) if all prerequisites exists in working memory. Thank you for help.