Physics 20 question

Two different springs are attached to a light, flexible rod as shown in the diagram. Spring A is pulled down and allowed to oscillate. Gradually spring B also starts to oscillate due to resonance as energy is transferred through the flexible rod. The spring constant for spring A is 30.0N/m and 20.0N/m for spring B. Determine the mass hanging from spring B is the mass on spring A is 300g