Who was the U21 Mens winner when Mike Marsden was the mixed restricted winner and Claire Nelson was the U21 Womens winner?
create table table_28211674_3 (u21_mens varchar, mixed_restricted varchar, u21_womens varchar, PRIMARY KEY (u21_mens))
select u21_mens from table_28211674_3 where mixed_restricted = "mike marsden" and u21_womens = "claire nelson"