(-8*10^11)^-2*(-8*10^11)^-3/[(-4*10^5)^-5*(2*10^6)]
=[1/(-8*10^11)^2]*[1/(-8*10^11)^3] / {[1/(-4*10^5)^5]*(2*10^6)}
={1/[(8^2*10^22)*(-8^3*10^33)]} / [(2*10^6)/(-4^5*10^25)]
=[1/(-8^5*10^55)] / [-1/(2^9*10^19)]
=[-1/(2^10*10^55)] * (-2^9*10^19)
=2*10^36