4.6. Consider the following history of six events in which operations span multiple ob- jects, assuming that A and B are initialized to 0: ev inv(write(1)) on A at P eva inv(sum()) on A, B at P eva resp(write()) from A at P ev inv(write(2)) on B at P cus resp(write()) from B at Ps eve resp(sum(2)) from A, B Show that this history is not linearizable but normal. at P2.