What would you do if you think you are given with the wrong task?

Sure i will go for discussing the task with an attention doing it

each employee in any institution has a defined job and everything he will to do , must be well defined - now, if you are giving with a wrong task, you have the wright to accept or to refuse but if you feel that you can achieve the task, so why not? at the end, cooperation leads to profits and everyone will benefit  

I think I should give me achance to try acheiving this task after telling my boss with this.If he said go ahead ,it is okay.Then I try to do my best to acheive my task successfuly.