this is a complete question!

0.. Consider the following class diagram that represents the relationships between people and articles. A person may be one of the authors or one of the reviewers of an article. Under certain conditions, a person may become a chief reviewer. Person -name: String review Article numberOfReviewed Articles: int -title: String isChief Reviewer: boolean author 0... +review(Article) Express the following in OCL. 1. An article must have at least one author. 2. A person cannot review an article co-authored by him. 3. A person cannot become chief reviewer unless he reviews at least twelve articles. 4. Post condition of the method Person: review(Article) 0..*