A particle of mass m moving with velocity u makes an elastic one-dimentional collision with a stationary particle of mass `m`. They come in contact for a very small time `t_0`. Their force of interaction increases from zero to `F_0` linearly in time `0.5t_0`, and decreases linearly to zero in further time `0.5t_0` as shown in figure. The magnitude of `F_0` is
A. `m u// T`
B. `2m u//T`
C. `m u//2T`
D. None of these
