The product of any two irrational numbers
Which one of the following is correct and which one is not correct? Give reasons.
1) If 'a' is a rational number and 'b' is irrational, then a+b is irrational.
2) The product of a non-profit rational number with an irrational number is always irrational.
3) Addition of any two irrational numbers can be rational.
4) Division of any two integers is an integer.