Consider the project balances in the table below for a typical investment project with a service life of four years.

n

A Subscript n

Project Balance

$0$

minus$$$$15$ comma $000$

minus$$$$15$ comma $000$

$1$

long dash

minus$13$ comma $500$

$2$

long dash

minus$12$ comma $500$

$3$

$3$ comma $625$

minus$10$ comma $500$

$4$

long dash

$100$

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Part $1$

$($a$)$ Determine the interest rate used in computing the project balance.

The interest rate is

$$

enter your response here$\%.($Round to the nearest whole$$ number.$)$