If a and b are positive integers and x = 4^a and y = 3^b, which of the following is a possible units digit of xy?  Select:
A) 0  B) 1  C) 5  D) 7  E) 8
The units digit of 4^a is either 4 or 6.   The units digit of 3^b is 3, 9, 7, or 1.   We can multiply the units digits together to see that the units digits of xy could be 2, 4, 6, or 8.   The answer is 8.
<result>E</result>
If a and b are positive integers and x = 4^a and y = 3^b, which of the following is a possible units digit of xy?