Answer :
To solve this problem it is necessary to use the concepts of Force of a spring through Hooke's law, therefore,
[tex]F = kx[/tex]
Where,
k = Spring constant
x = Displacement
Initially our values are given,
[tex]F = 685N[/tex]
[tex]x = 0.88 cm[/tex]
PART A ) With this values we can calculate the spring constant rearranging the previous equation,
[tex]k = \frac{F}{x}[/tex]
[tex]k = \frac{685}{0.88*10^-2}[/tex]
[tex]k = 77840.9N/m[/tex]
PART B) Since the constant is unique to the spring, we can now calculate the force through the new elongation (0.38cm), that is
[tex]F = kx[/tex]
[tex]F = (77840.9)(0.0038)[/tex]
[tex]F = 295.79N[/tex]
Therefore the weight of another person is 265.79N.