A \( 2 \, \text{meter} \) long scale with least count of \( 0.2 \, \text{cm} \) is used to measure the locations of objects on an optical bench. While measuring the focal length of a convex lens, the object pin and the convex lens are placed at \( 80 \, \text{cm} \) mark and \( 1 \, \text{m} \) mark, respectively. The image of the object pin on the other side of lens coincides with image pin that is kept at \( 180 \, \text{cm} \) mark. The \( \\% \) error in the estimation of focal length is:
