Solution
For this case we have the following values:
50, 55, 56, 57
68, 69, 73, 74,
74, 75, 76, 76,
78, 79, 82, 84
Then we can find the mean like this:

And then since we have 16 values we can find the medain with the following operation:
Median = (74+74)/2 = 74
Then the correct answer is:
b) Median = 74 and Mean = 70.38