Particle of masses m, 2m, 3m, …, nm grams are placed on the same line at distance l, 2l, 3l, …. , n/cm from a fixed point. The distance of centre of mass of the particles from the fixed point in centimetres is

Options

A. `frac(2n+1)l(3)`
B. `frac(l)(n+1)`
C. `frac(n(n^2 +1)l)`
D. `frac(2l)(n(n^2 +1))`