Answer
$B. ~105cm$
Work Step by Step
We can find the required focal length as
$f_{fluid}=[\frac{(n_{lens}-1)n_{fluid}}{n_{lens}-n_{fluid}}]f_{air}$
We plug in the known values to obtain:
$f_{fluid}=[\frac{(1.31-1)(1.36)}{1.31-1.36}](-12.5)=105cm$