"Their names were in the tenth letter."

[teabeadle]

Why is this "byla" and not "byly"? The subject (jména) is in plural.

[endless_sleeper]

Jméno is neuter. -a is used for neuter plurals.

[BoneheadBass]

I got this right using "dopise," while the correct answer uses "dopisu." Assuming that both are correct, is "dopisu" preferred? If so, why is that? Thanks!