Suppose the current values of accounts A and B are $1000 and $2000, respectively.
Suppose also that the two transactions are executed one at a time in the
order T1 followed by T2. This execution sequence appears in Figure 14.2. In the
figure, the sequence of instruction steps is in chronological order from top to
bottom, with instructions of T1 appearing in the left column and instructions of
T2 appearing in the right column. The final values of accounts A and B, after the
execution in Figure 14.2 takes place, are $855 and $2145, respectively. Thus, the
total amount ofmoney in accounts A and B—that is, the sumA + B—is preserved
after the execution of both transactions.