How large is the ROM? | What do you mean by ROM? | When the "Nokia Corporation" company produces phones, what is the average ROM size implemented into a certain phone.
SELECT T1.ROM_MiB FROM chip_model AS T1 JOIN phone AS T2 ON T1.Model_name   =   T2.chip_model WHERE T2.Company_name  =  "Nokia Corporation" order by T1.ROM_MiB desc limit 1
ROM size refers to ROM_MiB; average ROM size refers to AVG(ROM_MiB); produced by 'Nokia Corporation' refers to WHERE Company_name = 'Nokia Corporation';