Answer to part one: 544.20
Answer to part two: 196.17
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Work Shown:
Part One:
Plug P = 400, r = 0.08, n = 1 and t = 4 into the compound interest formula
A = P(1+r/n)^(n*t)
A = 400(1+0.08/1)^(1*4)
A = 400(1+0.08)^(1*4)
A = 400(1.08)^(1*4)
A = 400(1.08)^(4)
A = 400(1.36048896)
A = 544.195584
A = 544.20
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Part Two:
Follow the same steps as above but now use t = 8
A = P(1+r/n)^(n*t)
A = 400(1+0.08/1)^(1*8)
A = 400(1+0.08)^(1*8)
A = 400(1.08)^(1*8)
A = 400(1.08)^(8)
A = 400(1.85093021028188)
A = 740.372084112753
A = 740.37
Subtract this from the result in Part One
740.37 - 544.20 = 196.17