Time periods of oscillation of the same simple pendulum measured using four different measuring clocks were recorded as \( 4.62 \, \text{s} \), \( 4.632 \, \text{s} \), \( 4.6 \, \text{s} \) and \( 4.64 \, \text{s} \). The arithmetic mean of these readings in correct significant figure is:
