A clock with an iron pendulum beeps correct time at $15 ^{\circ}c$ what will be the error in time per day , if the room temperature is $20^{\circ}$?

Question

$\begin{array}{1 1}2.6 \;s \\ 6.25\;s \\ 1.3\;s \\ 3.1\;s \end{array}$