Following figure shows how a dummy activity can be used to represent two concurrent activities, A & B. By
definition, a dummy activity, which normally is depicted by a dashed arrow, consumes no time or resources.
Dummy activity is a hypothetical activity which takes no resource or time to complete. It is represented by broken
arrowed line & is used for either distinguishing activities having common starting & finishing events or to identify &
maintain proper precedence relationship between activities that are not connected by events