What are the input variable and the output variable?

number of rowers in a rowboat and the speed of the rowboat


input: number of rowers in the rowboat; output: speed of the rowboat


input: speed of the rowboat; output: number of rowers in the rowboat


input: number of rowboats; output: speed of the rowboat


input: number of rowers in the rowboat; output: the number of rowboats