What is the average ROM size of phones produced by the company named "Nokia Corporation"?
create table phone (chip_model varchar, company_name varchar, PRIMARY KEY (chip_model)); create table chip_model (rom_mib integer, model_name varchar, PRIMARY KEY (rom_mib))
select avg(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"