The campus also houses several performing arts facilities. The de Jong Concert Hall seats 1282 people and is named for Gerrit de Jong Jr. The Pardoe Theatre is named for T. Earl and Kathryn Pardoe. Students use its stage in a variety of theatre experiments, as well as for Pardoe Series performances. It seats 500 people, and has quite a large stage with a proscenium opening of 19 by 55 feet (17 m). The Margetts Theatre was named for Philip N. Margetts, a prominent Utah theatre figure. A smaller, black box theater, it allows a variety of seating and staging formats. It seats 125, and measures 30 by 50 feet (15 m). The Nelke Theatre, named for one of BYU's first drama teachers, is used largely for instruction in experimental theater. It seats 280.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What theater has a proscenium opening of 19m?
unanswerable