The lengths of 40 leaves of a plant are measured correct to the nearest millimetre, and the data obtained is represented in the following table: | Length (in mm) | Number of leaves | |----------------|------------------| | 118 - 126 | 3 | | 127 - 135 | 5 | | 136 - 144 | 9 | | 145 - 153 | 12 | | 154 - 162 | 5 | | 163 - 171 | 4 | | 172 - 180 | 2 | Find the median length of the leaves.