In an LCR circuit, capacitance is charged from C to 4C. For resonant frequency to remain unchanged, the inductance should be changed from L to

L/4

Since the resonant frequency did not change

                                                    f₁= f₂

                                               L₁C₁ = L₂C₂ = L₂(4C₁)

                                                  L₂ = L₁/4