2025 MSHS PRELIMS P1 Q16

\(\mathcal E=\{x:x\text{ is an integer and}\hspace{0.5em}0<x<11\}\), \(A=\{x:x\text{ is a factor of}\hspace{0.5em}20\}\), and \(B=\{x:x\text{ is a prime number}\hspace{0.15em}\}\).

1. List the elements of
   1. \(A\),[1]
   2. \(A\cup B\).[1]
2. Find \(n(A'\cap B)\).[2]