A scale model of a building with mass \( M \) is attached to a horizontal spring system with an effective spring constant \( k \) on a frictionless testing table. The system oscillates in simple harmonic motion with a period \( T_0 \). To simulate a different building design, weights are added to the model until the total mass is \( 2M \), and the spring system is replaced such that the new effective spring constant is \( 8k \). What is the new period of oscillation of the model?