R is a relation defined in Z by a Rb if and only ifab≥0, then R is

For a ∈ Z, we have a . a =a2≥0∴          a R a∀ a ∈ Z∴R is reflexiveLet a R b.∴            ab≥ 0, or ba ≥ 0  or  b R a∴ R is symmetric.Let a R b and b R c∴                            ab ≥ 0, bc ≥0⇒    (ab) (bc) ≥ 0 ⇒ b2 (ac) ≥ 0⇒       ac ≥ 0         (∵b2 ≥ 0) ∴ R is transitive.