$\"\"$

\

The time $\"\"$ .

\

Where

\

$\"\"$ is present value of truck, $\"\"$ is initial value of truck and $\"\"$ is annual rate of depreciation.

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Initial value of truck is $\"\"$ .

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a.

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Find how much time passed to purchase.

\

Truck present value is $\"\"$ and annual rate of depreciation is $\"\"$ .

\

Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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Change of base formula is $\"\"$ .

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Apply change of base formula to logarithm expression $\"\"$ .

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$\"\"$

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The time to purchase is $\"\"$ years.

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$\"\"$

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b.

\

Find how much time passed to purchase.

\

Truck present value is $\"\"$ and annual rate of depreciation is $\"\"$ .

\

Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

\

$\"\"$

\

Change of base formula is $\"\"$ .

\

Apply change of base formula to logarithm expression $\"\"$ .

\

$\"\"$

\

The time to purchase is $\"\"$ years.

\

$\"\"$

\

a. The time to purchase is $\"\"$ years.

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b. The time to purchase is $\"\"$ years.