PMP®:CAPM® - Leads and Lags

What are Leads and Lags?
Leads and Lags used in the project schedule development.

Leads
Lead is the amount of time a successor activity can be advanced with respect to a predecessor activity.

Lags
Lag is the amount of time a successor activity can be delayed with respect to a predecessor activity.

Activity dependencies with Leads and Lags 
Leads and Lags can be applied on any of the activity dependencies like Start to Start (SS), Start to Finish (SF), Finish to Start (FS) and Finish to Finish (FF).

In the above example, both red and blue activities are of 2 days duration. There is Finish to Start dependency between them. If you apply a Lag of 1 day(FS+1), blue activity will start after a gap of 1 day. If you apply a Lead of 1 day(FS-1), blue activity will start one day earlier before the completion of red itself, becoming a parallel activity.

Question

Answer: highlight between braces (3.The duration is only 3. For all other networks the duration is 5.)