4. If U ={x: x is a positive integers less than or equal to 20), A ={y:y is a prime number, B ={z :z is a factor of 18) and C ={p :p is a multiple of 3 less then 20), find the cardinality of the following sets by drawing the Venn diagram : i. n(AUB) ii. n(BUC) iii. n(AUBUC) iv. n(ABNC) v. n(A) vi. n (B) vii. n (C)​