I said for a) that w^2 = s/2m (since the spring stiffness intuitively I think must be 1/2 less than just a single spring)
b) w^2 = s/m
c) w^2 = 2s/m
Which gives a ratio of 0.5:1:2, which is "equivalent" to 1:2:4, but I'm not sure if this is the right approach.© BrainMass Inc. brainmass.com June 3, 2020, 8:39 pm ad1c9bdddf
Your solution is perfectly correct.
Perhaps I can supplement your intuitive guess about the spring stiffness by showing ...
This solution provides steps necessary to determine the values.