Finding standard deviation using only mean, min, max?

I want to find the standard deviation:

Minimum = 5
Mean = 24
Maximum = 84

Overall score = 90

I just want to find out my grade by using the standard deviation

Thanks,

A standard deviation cannot in general be computed from just the min, max, and mean. This can be demonstrated with two sets of scores that have the same min, and max, and mean but different standard deviations:

• 1 2 4 5 : min=1 max=5 mean=3 stdev≈1.5811
• 1 3 3 5 : min=1 max=5 mean=3 stdev≈0.7071

Also, what does an 'overall score' of 90 mean if the maximum is 84?