Calculate the net force of space shuttle

[runningirl]

Homework Statement

Right after clearing the launch tower, the space shuttle is accelerating upward at 6 m/s/s.

a) Calculate the net force on an 80 kg astronaut during this acceleration.
b) Calculate the force that the seat must exert on the 80 kg astronaut during this acceleration.
c) A few seconds later in the flight, the seat is exerting a force of 2080 N on the astronaut. At what rate is the space shuttle accelerating?

Homework Equations

f=ma

The Attempt at a Solution

for part a, i got 480 N.
for part B, i just added (80*9.8) to 480=1264.

i wasn't sure how to get part c...

 

[Doc Al]

What's the net force on the astronaut? What's his acceleration?