Total Cost: T
Fixed Cost: F
Variable Cost: V

Given: T =F+V

V decreased by 5%.

St1: F increased by 13%

Before Jan: T =F+V
In Jan: T = 1.13F + 0.95V

This statement is insuff as we need more information regarding the relationship between F and V.

St2: F =5V

T =6V.
This statement gives us a relationship between F and V but no information regarding any changes in F after January. So we cannot find out the changes made in Total Cost.

Combining 1 & 2

We have information regarding how F and V are related plus changes in F in January.

Before January: T = F + V
T = 6V (since F =5V)

In January: T = 1.13 F + 0.95V
F = 5V

So, T = 6.6V.

We can easily find the % change in Total cost.

Answer is C