In: Statistics and Probability
a) Define the standard random variable Z as 
______(1)
Then required probability is

b) WE know from normal table that 
 ____(2)
WE have to find a and b such that 
From (1) and (2) we get

Subtract the two gives
------------------------(3)
c) For the sample mean standard random variable Z is defined as
 n being sample size
Using b) part equation (3) we have
  
As b-a=3-(-3)=6
d) The sum of 10 rovers weights is 
 and standard deviation is 
The using normal table we have the required probability as
