Consider the following two transactions:

T₁₃: read(A);

read(B);

if A = 1 then B := B - 1;

write(B).

T₁₄: read(B);

read(A);

if B = 1 then A := A - 1;

write(A).

Let the consistency requirement be A = 1 or B = 1, with A = 1 and B = 1 as the initial values.

a. Show that every serial execution involving these two transactions preserves the consistency of the database.

b. Show a concurrent execution of T₁₃ and T₁₄ that produces a nonserializable schedule.

c. Is there a concurrent execution of T₁₃ and T₁₄ that produces a serializable schedule?