Q17

An audit of a banking transactions system has found that on an earlier occasion, two joint holders of account $A$ attempted simultaneous transfers of Rs. $10000$ each from account $A$ to account $B$. Both transactions read the same value, Rs.$11000$, as the initial balance in $A$ and were allowed to go through. $B$ was credited Rs.$10000$ twice. $A$ was debited only once and ended up with a balance of Rs. $1000$. Which of the following properties is/are certain to have been violated by the system?