Is anyone learned Coursera course named “R Programming” of Johns Hopkins Roger D. Peng?

Hi all,
Is anyone learned Coursera course named ?R Programming? of Johns Hopkins Roger D. Peng? 
I have one question of how to submit my homework.
Following is the request of the question:
pollutantmean <- function(directory, pollutant, id = 1:332) {
        ## 'directory' is a character vector of length 1 indicating
        ## the location of the CSV files

        ## 'pollutant' is a character vector of length 1 indicating
        ## the name of the pollutant for which we will calculate the
        ## mean; either "sulfate" or "nitrate".

        ## 'id' is an integer vector indicating the monitor ID numbers
        ## to be used

        ## Return the mean of the pollutant across all monitors list
        ## in the 'id' vector (ignoring NA values)
        ## NOTE: Do not round the result!
}
I have successfully come out the correct results. However, I do not know how to submit my homework step by step. 
I have attached one picture in this email, is anyone can help me out?
Thank you so much!