Write a Z specification to model a bank account system.

The following are the requirements:-

-A person can have more than one accounts

-An account can have upto two account holders

The system should allow following operations:-

-deposit (should allow depositing any amount into the account)

-withdraw (should allow withdrawal such that the minimum balance remains Rs. 1000)

-inquire (to check current balance of the account)

-open a new account