Answer:
200 N/m
Explanation:
Rearranging the formula F = kx, you find that k = F/x. For the first spring,
F = 36 N and x = 0.06 m (6 cm). So the spring constant, F/x, is 36N/0.06m = 600 N/m
For the second spring, F = 36 N and x = 0.09 m. F/x = 36N/0.09m = 400 N/m
The difference between these values is 200 N/m, and that's the answer.