The interest earned in the account after three years is $720.
The formula for simple interest= P×T × R/100
Principal (P) = $4000
Time( T) = 3 years
Rate(R) = 6%
interest(I)= 4000×3 × 6/100
I = 72000 ÷ 100
I = 720
Therefore, the interest earned in the account after three years is $720.
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