If x persons working x hours a day for each of y days produce y units of works, then the unit of work produced by y persons working y hours a day for each of x days is

• A.  \[{{y}^{2}}/{{x}^{2}}\]                   
• B.  \[{{y}^{{}}}/{{x}^{2}}\]          
• C.  \[{{y}^{2}}/{{x}^{3}}\]                   
• D.  \[{{y}^{2}}/x\]