Exercise 18.2.1 Below are two transactions, described in terms of their effect on two database elements A and B, which we may assume are integers Th: READ (A,t) t: t+2; WRITE CA ,t) READ Bit); t t*3; WRITE Bit) T2: READ B, s) s s* 2: WRITE B,s) READ A, s) s s 3; WRITE (A, s) CHAPTER 18. CONCURRENCY CONTROL 896 We assume that, whatever consistency constraints there are on the database, these transactions preserve them in isolation. Note that A B is not the consistency constraint. a) It turns out that both serial orders have the same effect on the database, that is, (Th,T2) and (T2,T1) are equivalent. Demonstrate this fact by showing the effect of the two transactions on an arbitrary initial database State. b) Give examples of a serializable schedule and a nonserializable schedule of the 12 actions above. c How many serial schedules of the 12 actions are there? d) How many serializable schedules of the 12 actions are there