De Morgan’s law
\((\bigcup\limits_{r = 1}^{n} A_r)' = \bigcap\limits_{r=1}^{n} (A_r)'\)
\((\bigcap\limits_{r = 1}^{n} A_r)' = \bigcup\limits_{r=1}^{n} (A_r)'\)
\((\bigcup\limits_{r = 1}^{n} A_r)' = \bigcap\limits_{r=1}^{n} (A_r)'\)
\((\bigcap\limits_{r = 1}^{n} A_r)' = \bigcup\limits_{r=1}^{n} (A_r)'\)