Five persons are standing in a queue, one of two persons at the extreme end is a doctor and the other is engineer. An advocate is standing to the right of the student. An Author is to the left of the engineer. The student is standing between the doctor and advocate. If the advocate and engineer exchange their positions and also the author and the student, then who will be standing to the left of the author?

Engineer

Five persons are standing in a queue, one of two persons at the extreme end is a doctor and the other is engineer. An advocate is standing to the right of the student. An Author is to the left of the engineer. The student is standing between the doctor and advocate. If the advocate and engineer exchange their positions and also the author and the student, then who will be standing to the left of the author?

I) one of two persons at the extreme end is a doctor and the other is engineer. 

=> Doctor - Student - Advocate - Engineer - Engineer

II)  An advocate is standing to the right of the student. An Author is to the left of the engineer.

=> Doctor - Student - Advocate - Author - Engineer

III) the advocate and engineer exchange their positions and also the author and the student

=> Doctor - Student - Engineer - Author - Advocate 

Thus, "Engineer " will be standing to the left of the author.