If the operation € is defined for all x and y by the equation x € y = 2*x*y, then 9 € (4 € 5) = Choose the correct answer:
A) 80 B) 720 C) 760 D) 840 E) 860
working inside out,   (4 € 5) = 2*4*5= 
<gadget id="calculator">2*4*5</gadget>
<output>40</output>
40   9 € 40= 2*9*40= 
<gadget id="calculator">2*9*40</gadget>
<output>720</output>
720   Hence, answer is 720
<result>B</result>
If the operation € is defined for all x and y by the equation x € y = 2*x*y, then 9 € (4 € 5) =