Assume a file sales.txt is in the default location. Write C# statement(s) to calculate the sum of all sales numbers in sales.txt and add the additional line The total sales is _____. to the file sales.txt. You should put the total sales number in the currency format in the blank. For example, if there are two sales number in the sales.txt, i.e., 34.56 and 12.23. You should add the sentence The total sales is $46.79. in the sales.txt file.