A very short 100 kg acrobat steps off a 10 m high platform and starts falling. The acrobat falls 9 m, then encounters a 1 m long spring connected at
one end to the ground below.
(a) What’s the spring constant so the acrobat just touches the ground (that is, so the spring contracts 1 meter)?

The spring-with-acrobat system rebounds
and launches the acrobat back into the air.
(b) How high off the ground does the acrobat go above the ground before falling back?

I got 1.765 x 10^4 N/m for the spring constant, but I'm not sure how to do the second part.

Question

A very short 100 kg acrobat steps off a 10 m high platform and starts falling. The acrobat falls 9 m, then encounters a 1 m long spring connected at
one end to the ground below. 
(a) What’s the spring constant so the acrobat just touches the ground (that is, so the spring contracts 1 meter)? 

The spring-with-acrobat system rebounds
and launches the acrobat back into the air. 
(b) How high off the ground does the acrobat go above the ground before falling back?

I got 1.765 x 10^4 N/m for the spring constant, but I'm not sure how to do the second part.