A frequency table gives the number of weather stations in each temperature class in degrees Celsius as follows: 0 to 10 has 1 station, 10 to 20 has 2, 20 to 30 has 3, 30 to 40 has 4, 40 to 50 has 5, 50 to 60 has 4, 60 to 70 has 3, 70 to 80 has 2 and 80 to 90 has 1, giving 25 stations in all. The number of stations that recorded a temperature less than 40 degrees Celsius is: