The best firm for the Appliance manufacturer for the repair work is Firm 2 .
In the question , 
it is given that , 
An appliance manufacturer wants to contract with a repair shop to handle authorized repairs in Indianapolis .
The acceptable range of the repair time is 50 minutes to 90 minutes.
the mean repair time for firm 1 = 74 minutes and standard deviation of 4 minutes . 
the mean repair time for firm 2 = 72 minutes and standard deviation of 5.1 minutes .
the range is calculated using the formula 
Range = Mean ± Standard Deviation 
So , for firm 1 , 
the Range = 74 ± 4 
= 74  4       and      74 - 4
 4       and      74 - 4
= 78     and   70
the range for firm 2 is 
= 72 ± 5.1
= 72  5.1      and      72 - 5.1
 5.1      and      72 - 5.1
= 7.1        and       66.9  
The second company has a lower range and it should be preferred . 
Therefore ,  The best firm for the Appliance manufacturer for the repair work is Firm 2 .
Learn more about Standard Deviation here 
brainly.com/question/23611887
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|a| = -a for a < 0
|a| = a for a ≥ 0
examples:
|-1| = -(-1) = 1; |-4| = -(-4) = 4; |-0.1| = 0.1; |-109| = 109
|7| = 7; |19| = 19; |0| = 0
- |-7 + 4| = - |-3| = - (3) = -3
Answer: -|-7 + 4| = -3
 
        
                    
             
        
        
        
The properties of exponents would help solve exponential equations by creating an expression that can be simplified easily. It elps in simplfying a certain equation. It tells us how are terms that contain exponents can be added, subtracted, divided and multiplied. For addition, terms having the same can only be added. This would be also true for subtraction. For example, we have x^2 + y^3, these terms could not be added since they have different base. For multiplication, we can readily multiply these terms and add the exponents of the terms with the same base, x^2(y^2)(x) = x^3y^2. For division, they can also be divided readily but, terms with the same base, the exponents are to be subtracted, x^3 / x^2 = x.
        
             
        
        
        
For graphing, the desmos graphing calculator is a big help :))