The consolidated data of a spot speed study for a certain stretch of a highway is given in the table.
| Speed range $(\mathrm{kmph})$ | Number of observations |
| $0-10$ | $7$ |
| $10-20$ | $31$ |
| $20-30$ | $76$ |
| $30-40$ | $129$ |
| $40-50$ | $104$ |
| $50-60$ | $78$ |
| $60-70$ | $29$ |
| $70-80$ | $24$ |
| $80-90$ | $13$ |
| $90-100$ | $9$ |
The "upper speed limit" (in $\mathrm{kmph}$) for the traffic sign is
- $50$
- $55$
- $65$
- $70$