I need help with a spring problem:

Two identical springs hung from a ceiling have different masses. The first spring is 1 kg with a total length of 6 cm. The second spring is 1.5 kg and is 7 cm in length. The displacement between the two springs is 1 cm. Find the spring constant k.

(A) 2 N/cm

(B) 5 N/cm

(C) 10 N/cm

(D) 20 N/cm

I started solving each equation for k, but ended up with different values. Thanks in advance.

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