A mistake was committed by an acountant. What are the responsibilities of (a)Accountant.(b)Finance Manager.(c)Internal Auditor.(d)External Auditor?

The Accountant after discovering the error / mistake should immediately rectify it. Proper procedure - example passing the journal entry(ies) duly checked and authorised.

The Finance Manager after discovering the error / mistake should immediately notify the Accountant to rectify it. 

The Internal Auditor should highlight to the Finance Manager the error and ensure that rectification was carried out. The Internal Auditor should also find out how and why the mistake happened and recommend to the management internal control procedures so that such mistake does not happen again.

The External Auditor should notify the management the mistake. If the amount involved is material, it can highlight this in the audit report. Nevertheless the External Auditor should present the figures after rectifying the mistake

Depend on what type of mistake done by accountant.

For accountant he should rectify this mistake.

For Internal Auditor if the mistake arises due to internal control weakness then in that case internal auditor should review the internal control processes to make sure that such mistakes couldn't happen again and suggests the corrective action.

Finance manager should take necessary corrective actions with regards to policy & procedures set by management.

External auditor should asses that if this mistake has a material impact on the true & fair presentation of statement of accounts then he should highlight this mistake in the management letter.

The Accountant should bring it to the attention of the manager to whom he is reportable.

The responsibilty of the Finance Manager is to look into the matter, assess the consequences of the mistake and take actions as per the policy established by the management.

Internal auditor once become aware of the mistake should inquire the reason contributed towards the happening of such mistake and suggest the improvement in the control environment and control procedures to avoid its occurance in future. Also he ensures that the proper steps has been taken as per the Company Policy to handdle the issue.

External auditor once become aware of such instance will assess its impact, if any, on the financial statements, the reliance obtained on the controls and their effectiveness and overall impact on the audit report. Further, he also consider his responsibility to inform third party (like; regulator) for such instance. 

A Mistake is commited by an accountant . The responsibilities of an accountant to learn the appropriate mistake from an Internal Auditor....

I agree what the answer of Mohd Shariff Ismail , very good answer.