in eoq we are trying to minimize the holding and ordering cost. And we are only considering the variable cost. So when question says holding cost per unit…..it mainly refers to those holding cost which vary with units and not those cost which are fixed like rent of warehouse ,tough it is a part of holding cost but its not considered here.
Similarly in ordering cost we are considering the variable cost per order like transportation cost, and not considering the personnel cost who place the order cause its salary remain fixed irrespective of no. of orders he placed.