Answer:
90000N
Explanation:
Using gravitational law, F = G(m1)(m2)/r^2, where m1 is the mass of the earth = 5.9742x10^24kg, m2= mass of the man = 900/9.81 = 91.74kg, the r is the distance between the man and the center of the air and it is equal to (6378km+9000m = 6387km), this computation is almost equal to the answer when the solution you use is ratio and proportion.
