What is the greatest prime factor of 12!11! + 11!10!?	Choices:
A) 7 B) 11 C) 13 D) 17 E) 19
Soln:   12!11!+11!10!= 12*11*10!*11*10!+11*10!*10!=10!*10!*11(11*12+1)=10!*10!*11*133=10!*10!*11*19*7   greatest prime factor in 10! is 7 which is less than 19.   So Ans is 19
<result>E</result>
What is the greatest prime factor of 12!11! + 11!10!?