Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| System | Year Introduced | S-100 slots | Internal Floppy Disk | Internal Hard Disk |
| --- | --- | --- | --- | --- |
| Z-1 | 1976.0 | 21.0 | n/a | n/a |
| Z-2 | 1977.0 | 21.0 | n/a | n/a |
| System Zero | 1980.0 | 4.0 | n/a | n/a |
| System One CS-1 | 1981.0 | 8.0 | 2 x 5-inch | n/a |
| System One CS-1H | 1981.0 | 8.0 | 1 x 5-inch | 5 megabytes |
| System Two Z-2D | 1978.0 | 21.0 | 2 x 5-inch | n/a |
| System Two Z-2H | 1980.0 | 12.0 | 2 x 5-inch | 11 megabytes |
| System Three | 1978.0 | 21.0 | 4 x 8-inch | n/a |
Question:
Which system introduced earlier than 1981 has an internal hard disk of 11 megabytes and less than 21 s-100 slots?
Answer:
System Two Z-2H