LetT $=\{($a$,$b$)|$a$,$b in N$,$ab $=5$k forsomenaturalnumberk$\}$bearelationonN$.$

a$)$ Write two elements in the set T $.$

b$)$ Which of the reflexivity, symmetry, antisymmetry, and transitivity do$($es$)$

not hold for T $?$ Justify your answer.