Two springs, of force constants $k_1$ and $k_2$ are connected to a mass m as shown. The frequency of oscillation of the mass is $f$. If both $k_1$ and $k_2$ are made four times their original values, the frequency of oscillation becomes : <br>

Question

( A ) $4f$
( B ) $f/2$
( C ) $f/2$
( D ) $2f$