Question 4: Z Exercise: (4 marks] Consider the following Z specification for a system which records bank accounts: a. Identify the state invariant. Briefly describe what it states. b. Write the GetBalance schema. It specifies an operation that takes an account as input and returns the corresponding balance. Assume that the account is in known. c. Write the IsSavings Account schema. It specifies an operation that takes an account as input and returns its type according to the balance amount, if the balance is more than or equal 10000 then it will return the type as Savings otherwise it is considered Current. Assume that the account is in known. Question 4: Z Exercise: (4 marks] Consider the following Z specification for a system which records bank accounts: a. Identify the state invariant. Briefly describe what it states. b. Write the GetBalance schema. It specifies an operation that takes an account as input and returns the corresponding balance. Assume that the account is in known. c. Write the IsSavings Account schema. It specifies an operation that takes an account as input and returns its type according to the balance amount, if the balance is more than or equal 10000 then it will return the type as Savings otherwise it is considered Current. Assume that the account is in known