Relational Data Model

Consider a relation $R(A,B,C,D,E)$ with the following dependencies:

$ABC$

$CDE$

$DEB$

a$)$ Is $AB$ a candidate key of this relation?

b$)$ If not, is ABD $?$ Explain your answer using the closure of attributes.

Consider the following relation:

STUDENT $($SID$,$ Lname, MajorDeptID, MajorDeptName, CourseID, instructorID, Grade$)$

Assume SID, courseID