Question 3 (24 marks) This question is based on Sections 3 and 4 of Block 2. It assesses your ability to understand and write representations of constraints, and to manipulate relations and relational operators. This question refers back to the relational model of Question 2. (a) Assuming the relation Event has alternate key (CustomerCode, Date), express the corresponding constraint in natural language. (2 marks) (b) Write relational expressions to express the following constraints: (i) A venue used for a particular event must have a capacity greater than or equal to the number of people expected at that event. (4 marks) (ii) An event cannot have a luxury caterer in an economy venue. (5 marks) (iii) An entertainer cannot perform at more than one event on the same date (6 marks) (c) Write relational expressions which give: (i) The code of each event where either there is no entertainer or where the number of people expected is fewer than 50. (3 marks) (ii) The code of each comedian who has not yet participated in an event. (4 marks)