Create a package which includes a function to return a square of a number if it is positive else return an error message to the user. 

Create a package which contains function to ask the user to enter the student’s marks and determine the GRADE according to the following criteria. >90 A >80AND <90 B >70AND <80 C >60 AND<70 D <60 F

Write a trigger to ensure that no employee of age less than 25 can be inserted in the database. 

Given relation R (A,B,C,D) and the following FD’s. Identify the candidate key for R and highest normal form B->C, D->A