Answer
(a) The resonance frequency will decrease.
(b) $77.5Hz$
Work Step by Step
(a) As we know, $f=\frac{1}{2\pi \sqrt{LC}}$. This equation shows us that resonance frequency is inversely proportional to L and C. That is why the resonance frequency will decrease, if we double L and C.
(b) We know that
$f=\frac{1}{2\pi \sqrt{(2L)(2C)}}$
$\implies f=\frac{1}{2\pi \sqrt{4LC}}$
$\implies f=\frac{1}{2}(\frac{1}{2\pi \sqrt{LC}})$
$f=\frac{1}{2}f_{\circ}$
We plug in the known values to obtain:
$f=\frac{1}{2}(155)=77.5Hzz$
