Let Aj, 1 < i < 5, be the domains for a table D A1

Question:

Let Aj, 1 < i < 5, be the domains for a table D ⊂ A1 × A2 × A3 × A4 × A5, where A1 = {U, V, W, X, Y, Z} (used as code names for different cereals in a test), and A2 = A3 = A4 = A5 = Z+. The table D is given as Table 5.7.
(a) What is the degree of the table?
(b) Find the projection of D on A3 × A4 × A5.
(c) A domain of a table is called a primary key for the table if its value uniquely identifies each list of D. Determine the primary key(s) for this table.