Approximating the mean and standard deviation

#1
Hi,
I just started my statistics class and I've been having a little trouple grasping it. I just don't know where to start with this and my book is a little confusing.
Here's the problem:

A sample of college students was asked how much they spent monthly on a cell phone plan (to the nearest dollar). Approximate the mean and standard deviation for the cost.

Monthly cell phone plan cost ($)..........................Number of Students
10-19..........................................................................8
20-29.........................................................................16
30-39.........................................................................21
40-49.........................................................................11
50-59..........................................................................4



I don't need the answer, I'd like to find it for myself. I would just like to know how to do these sort of problems. I would appreciate it so much if I could get some help.
Thank you for your time,
Nicole
 
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