Answer
a) frequency increases by a factor of 2
b) 1.07
Work Step by Step
(a) As we know that $f\propto T$
$\implies \frac{f_1}{f_2}=\frac{T_1}{T_2}$
We plug in the known values to obtain:
$\frac{f_1}{f_2}=\frac{20}{40}=\frac{1}{2}$
Thus the final frequency is twice the initial frequency.
(b) As $T_1=273.15+20=293.15K$
and $T_2=273.15+40=313.15K$
Now $\frac{f_1}{f_2}=\frac{T_1}{T_2}$
We plug in the known values to obtain:
$\frac{f_2}{f_1}=\frac{313.15}{293.15}=1.07$
