[Eseny]

Hello everyone;I started spanish about 5 weeks ago and I have a question from my book.
I finished some exercises about reflexive verb -ir- (to go) and the right answers are shown at the end of the book like below;

Me voy al trabajo I go to work
Tu te vas al colegio You go to school
Mi padre se la oficana My father goes to ofice

But why this sentence below is not in reflexive form even though same structure.
Ustedes van a la oficana (This is shown as right answer,not reflexive form)
Why not; Ustedes se van a la oficana (I selected this as a right reflexive form)

What is the difference between the 4th sentence and the first three.Is this a mistake in the book? Thanks in advance.