Question $2$: Let M and N be two sets described below. Find intersection of M $\backslash$cap N and $|$N$|.$

M $=\{$x : x is natural number and multiple of $3\}$

N $=\{$x : x is a positive prime number less than $19\}$

a$.$ M $\backslash$cap N

b$.|$N$|$