conservation of linear momentum

Neutrons in a nuclear reactor have the Kinetic energy $\displaystyle 6.0\times10^{-13}$J . The kinetic energy of the neutron is reduced to $\displaystyle 6.0\times10^{-21}$ by a series of collision between the neutron and carbon nuclei in the moderator . On average , the fractional loss of the kinetic energy of the neutron after each collision is 0.14 . how many collisions does a neutron experience in the process ?

My working :

Let the initial Kinetic energy : $\displaystyle E_o$

Kinetic energy after 1 collision = $\displaystyle (1-0.14)E_o$

After n collisions , the kinetic energy will be

(1) $\displaystyle n(0.86)E_o$ or

(2) $\displaystyle (0.86)^nE_o$

Which one is the correct one and why is it so ?? Thanks for your time .