Whats 4 times 5 1/8 (find each product mentally. show the steps you used)show work )

22 points algebra 1//sum and product of rational and irrational numbers. dont have to do all 4 if could much : )) write an example: 1) how the product of two identical irrational numbers can be a rational number. 2) how the product of two different irrational numbers can be a rational number. 3) write a quotient of intergers that is not a real number. 4) is the set of positive irrational numbers closed for the operation of division? if not give a counter example.