They are essentially asking us to solve:

Solving this equation for x tells us that it will take around 80.1 years for the materials in the vault to reduce to 357 pounds.
The slope is -4/1. Hope this helps
Complete question :
Each state imposes its own excise tax on gasoline. Suppose, for example, that the state of Massachusetts imposes a state gasoline tax of $0.26 per gallon. Suppose further that an average of 1,022,000 gallons of gasoline per day were sold in Massachusetts in 2010. The average revenue from gasoline tax in 2010 is approximately?
Answer:
$265,720
Step-by-step explanation:
Given that:
State gasoline tax = $0.26 per gallon
Average number of gasoline sold per day = 1,022,000 gallons
. From the availabke information given :
Revenue generated = gasoline tax per gallon multiplied by the average number of gallons sold
= $0.26 * 1,022,000
= $265,720
L = 2 W
B = L x W = 2 W²
Side Area = 2 W H + 2 L H = 2 H ( W + L ) = 6 H W
V = 2 W² H = 10
H = 5 / W²
Cost = 15 * 2 W² + 9 * 5/W
= 30 W² + 270/ W
C ` = 60 W - 270 / W²
= ( 60 W² - 270 ) / W² = 0
60 W² = 270
W ² = 270 : 60
W² = 4.5
W = √ 4.5 = 2.12
Cost (min) = 15 * 2 * 4.5 + 30 / 2.12 = 135 + 14.15 = $149.15
Answer: The cost of materials for the cheapest such container is $149.15.
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