Alfonso can do a certan job in 1 hour. His brother can do the same job in 1 hour however, their older sister Josefa can do this jobin 45 minute. If all three work together, how long will it take them to do the job?

Which of the following statements is true? a. the irrational number system is not closed under multiplication, because the product of two irrational numbers is always a rational number. b. the irrational number system is not closed under multiplication, because the product of two irrational numbers is not always an irrational number. c. the irrational number system is closed under multiplication, because the product of two irrational numbers is always an irrational number. d. the irrational number system is closed under multiplication, because the product of two irrational numbers is always a rational numbers. reset submit