There are 10 weekdays from May 16 to May 26, inclusive.
To complete 39 assignments, you would need to do an average of 3.9 assignments per weekday.
However, since you can't do a fraction of an assignment, you would need to do either 3 or 4 assignments per weekday.
To do 3 assignments per weekday, you would complete a total of 30 assignments (3 x 10 weekdays) by May 26, leaving 9 assignments unfinished.
To do 4 assignments per weekday, you would complete a total of 40 assignments (4 x 10 weekdays) by May 26, which is more than enough to complete the 39 due assignments.