Question 1192422
The range is 15 gm and 5 gm are below 1000 gm. So a. is 5/15 or 1/3 probability. 
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The mean is in the middle 1or 1002.5 gm  as you have.
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V(x)=(b-a)^2/12=225/12=18.75 as you have.