The effective interest rate is
and the interest is 
Further explanation:
The compound interest rate formula can be expressed as follows,

Here, A represents the amount, P represents the principal amount, i represents the interest rate and n represents the time.
The interest rate in a year is known as the effective interest rate.
The relationship between effective interest rate and nominal interest rate can be expressed as follows,

Here, i represents the effective interest rate,
represents the nominal interest rate, n represents the period of interest rate.
Given:
The nominal interest rate is
in a 13 week treasury bill.
The amount of Treasury bill is 
Explanation:
There are 52 weeks in a year.
The value of n can be calculated as follows,

The effective interest rate can be calculated as follows,

The interest can be calculated as follows,

The effective interest rate is
and the interest is 
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Answer details:
Grade: High School
Subject: Mathematics
Chapter: Compound interest
Keywords: Principal, invested, interest rate, account, effective interest rate, total interest, 8\% Treasury bill, nearest hundredth percent, amount.