user: Question: What is the average frequency in MHz for stations with an ERP W of 170?
Columns: ['Call sign', 'Frequency MHz', 'City of license', 'ERP W', 'Class', 'FCC info']
Types: ['text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['K297AL', 107.3, 'Dighton, Kansas', 170.0, 'D', 'FCC']
SQL:

assistant: SELECT AVG("Frequency MHz") FROM "Table" WHERE "ERP W" = 170.0;