ClassFrequencyCumulativefrequency−0.5−5.513135.5−11.5102311.5−17.5153817.5−23.584623.5−29.51157
Given, classes are not continuous, so we make continuous by subtracting 0.5 from lower limit and adding 0.5 to upper limit of each class.
Here, N2=572=28.5, which lies in the interval 11.51-17.5.
Hence, the upper limit is 17.5