user: Question: what is the highest frequency mhz with the call sign W292CU?
Columns: ['Call sign', 'Frequency MHz', 'City of license', 'ERP W', 'Class', 'FCC info']
Types: ['text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['W294AJ', 106.7, 'Charlottesville, Virginia', 21.0, 'D', 'FCC']
SQL:

assistant: SELECT MAX("Frequency MHz") FROM "Table" WHERE "Call sign" = 'W292CU';