After the execution of the following statements, what are in s$?$

Set s $=$ new HashSet$()$;

s$.$add$("$hello$")$;

s$.$add $("$bye$")$;

s$.$add$("$hello$")$;

Set t $=$ new HashSet$()$;

t$.$add$("123")$;

s$.$addAll$($t$)$;