Mike, a Member of an Employees' Union, Negotiates His Salary

Mike, a member of an employees' union, negotiates his salary and reimbursement package directly with the employer. However, this was contrary to the collective union policy. Which of the following is legally permissible in this scenario?

A) The other members of the union can sue Mike and claim monetary damages.
B) Mike can be sued by the union for by passing it and contracting directly with the employer.
C) Mike and the employer are well within their rights to sign a contract.
D) The employer is liable to nullify the contract made with Mike.