Ten students took a statistics final and their scores were 78.5; 80.1; 74.9; 85.3; 89.5; 84.4; 83; 78.1; 77.1; 81.9. Calculate the standard deviation of the dataset:
a) 81.28
b) 81
c) 4.174
d) 4.4
e) 812.8