From 6 positive numbers and 6 negative numbers, how many groups R of 4 numbers, yielding a positive product, can be formed?
Select:
A) 720
B) 625
C) 30
D) 960
E) 255
Potential combinations of 4 numbers that will yield positive product   ++++ 4C6   ---- 4C6   ++-- 2C6*2C6   4C6 + 4C6 + 2C6*2C6   R=15 +15 + 15*15= 
<gadget id="calculator">15 +15 + 15*15</gadget>
<output>255</output>
255=255
<result>E</result>
From 6 positive numbers and 6 negative numbers, how many groups R of 4 numbers, yielding a positive product, can be formed?