please explain with stepsespecially how to get the error in T

Thanks in advanced

Exercise 9: A simple pendulum can be used to measure the gravitational acceleration g. If the oscillation angle is very small, then the period of oscillation T is related to the length of the pendulum according to T= 25C = 21 For a pendulum of length L = 60.0 + 0.2 cm, 10 different measurements of the period in seconds are found to be 1.58 1.57 1.56 1.57 1.53 1.55 1.55 1.55 1.54 1.60 Find the value of gravitational acceleration and estimate its error.