Answer
(a) $_{11}C_4=330$
(b) $_{66}C_4=720,720$
Work Step by Step
(a) $_{11}C_4=\frac{11!}{(11-4)!~4!}=\frac{11\times10\times9\times8\times7!}{7!\times4\times3\times2\times1}=330$
(b) $_{66}C_4=\frac{66!}{(66-4)!~4!}=\frac{66\times65\times64\times63\times62!}{62!\times4\times3\times2\times1}=720,720$
