user: Question: What is the highest ERP W of the translator with a call sign of W284AV?
Columns: ['Call sign', 'Frequency MHz', 'City of license', 'ERP W', 'Class', 'FCC info']
Types: ['text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['W283AN', 104.5, 'Altamonte Springs, Florida', 10.0, 'D', 'FCC']
SQL:

assistant: SELECT MAX("ERP W") FROM "Table" WHERE "Call sign" = 'W284AV';