CREATE TABLE table_name_37 (watts INTEGER, city_of_license VARCHAR(255), class VARCHAR(255), frequency VARCHAR(255))
How many Watts has a Class of a, and a Frequency of 91.5 fm, and a City of license of elkhart, kansas?
    
SQL: SELECT MIN(watts) FROM table_name_37 WHERE class = "a" AND frequency = "91.5 fm" AND city_of_license = "elkhart, kansas"