Answer:
F = 7.8  10³ N
Explanation:
For this exercise we will use the law of universal Gravitational
     F = G M m / r²
for initial conditions
    F₀ = G M m₀ / r₀²
    Â
   They tell us that the mass changed at m = 2m  distance at r = 0.8r₀
we substitute
   F = G M 2m₀ / (0.8 r₀) ²
   F = (GM m₀/ r₀²)  [tex]\frac{2}{0.64}[/tex]
   F = 3.125 F₀
  Â
let's calculate
   F = 3.125 2.5 10³
   F = 7.8125 10³ N