$4.$ Draw the following tree binary relationships: $($a$)$ A patient must be assigned to only one doctor, and a doctor can have many patients; $($b$)$ An employee is assigned to one office, and each office may be assigned to one and only one employee; $($c$)$ A product is comprised of at least three components, and components are used to make different products. Indicate minimum and maximum cardinalities, degree and optional$/$mandatory nature of each relationship. $[15$ points$]$