Answer:
Question 4 appears somewhat misleading"
The gravitational force on the astronaut is:
F = G M m / R^2
F = (6.67 E-11 * 5.98 E24 * 75) / (1.26 E7)^2 = 187 N
This would be the gravitational force on the astronaut; however the astronaut is in orbit with a centripetal force of 187 N and would feel "no" net force.
Since F = m a m = 187 / 9.8 = 19 kg which would be the astronaut's normal "weight" at that altitude.
Note that 1.26 * 10E7 equals about 2 * 6.4 * 10E6, squared gives a total of around 4 so the astronaut's true weight is about 76 / 4 = 19 kg at that altitude.
