A table in a database has three columns: a, b, and c. In row…

A table in a database has three columns: a, b, and c. In row-oriented storage, each full row occupies approximately 20 bytes. In a columnar storage format, column a is compressed to about 2 bytes per value. If a query reads aggregates column a, how much of the I/O cost can be saved compared to reading full rows in row-oriented storage?