The reduced levels of points, 30 metres apart along the longitudinal section of a road portion between chainages 5 and 9 are shown in the given figure. If there is a uniform up-gradient of the road 120 in 1, the chainage of the point with no filling or cutting is

• (6 + 15) chains
• (6 + 12) chains
• (6 + 18) chains
• None of these.