Calculate the mean plant height, the variance and the standard deviation for 10 plants that have the following heights: 5 cm, 6 cm, 6 cm, 7 cm, 7 cm, 7 cm, 8 cm, 9 cm, 9 cm, and 10 cm.
a) mean: 7. 4 cm variance: 25 cm² standard deviation: 1. 6 cm
b) mean: 7 cm variance: 3. 5 cm2 standard deviation: 1. 9 cm
c) mean: 7. 4 cm variance: 25 cm2 standard deviation: 1. 9 cm
d) mean: 75 cm variance: 3. 5 cm2 standard deviation: 1. 6 cm