A year later, Mia gained $400.
Mia invests in an index fund= $5000
The share price of the fund has grown by 8% after a year.
So, one year later Mia's investment would also increase by 8% since her invested share value has grown by 8%.
Hence, the amount of share would be = ($5000 + 8% of $5000) =($5000+$5000*8/100) = ($5000+$400) = $ 5400
Therefore, Mia's gain is $400.
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