suppose but and so there exists auniquesuch that but then: therefore and hence contradiction.

we have and thus since the first part of the problem gives us:b. show that bab = b.

let so there exists such that the claim is that so let then and hence therefore by the first part of the problem.c. show that R has unity.

also by the second part, and thus which gives us thus

let so there exists such that and thus which gives us:d. show that R is a division ring.