Answer:
He earned a lower interest rate than he expected
Option 1800 interest rate 6,06% expected
Option 1680 interest rate 5,33% real amount
Explanation:
Option 1680 interest rate 5,33%
1 1.000 5,33% 53 1.053
2 1.053 5,33% 56 1.109
3 1.109 5,33% 59 1.169
4 1.169 5,33% 62 1.231
5 1.231 5,33% 66 1.296
6 1.296 5,33% 69 1.366
7 1.366 5,33% 73 1.438
8 1.438 5,33% 77 1.515
9 1.515 5,33% 81 1.596
10 1.596 5,33% 85 1.681
Option 1800 interest rate 6,06%
1 1.000 6,06% 61 1.061
2 1.061 6,06% 64 1.125
3 1.125 6,06% 68 1.193
4 1.193 6,06% 72 1.265
5 1.265 6,06% 77 1.342
6 1.342 6,06% 81 1.423
7 1.423 6,06% 86 1.510
8 1.510 6,06% 91 1.601
9 1.601 6,06% 97 1.698
10 1.698 6,06% 103 1.801