$$A, B, C$$ and $$D$$ live in the same block of apartment that has $$18$$ level. Their name are Zachary, Yvonne, Xavier and Waylon.  We know that:  (1) $$A$$ stays in an unit that located higher than $$C$$, but lower than $$D$$  (2) $$B$$ stays in an unit that is lower than Xavier\textquotesingle s unit  (3) $$D$$ stays in an unit that is $$5$$ times Yvonne\textquotesingle s unit  (4) If Zachary moves to two level above his unit, the difference in level between his unit and Xavier\textquotesingle s unit is equal to the difference of his unit with Waylon\textquotesingle s unit.  (5) The level that Zachary stays is the sum of the level Yvonne and Xavier stay.  Based on the information above, do you know who is which level does $$A$$ stays in? 
Overseas Competition->Knowledge Point->Combinatorics->Logical Reasoning