Trade Sanctions and Segmentation

There are 100 countries in the World. Demand in country number $i$ for natural gas is given by $D_i(p_i) = 100i - p_i$, while its supply is given by $S_i (p_i) = ip_i$.

(a) (5 rp) Find equilibrium prices $p_i ^*$ when countries do not trade with each other