To answer this question we will use the following formula for annual simple interest:
![A=P(1+rt),](https://img.qammunity.org/2023/formulas/mathematics/college/9afoltzst3p4hs9nc5rnhcqrzw6d9rl1jy.png)
where P is the initial amount, r is the annual interest rate, and t is the time in years.
Now, if he invested $1000 in a 5.5% interest account, then after 1 year he will earn:
![A_1=1000(1+0.055*1)=1055.](https://img.qammunity.org/2023/formulas/mathematics/college/qkghrfufe6n3i7cwsjaovjw2dmscb2mbqj.png)
Since he invested the remaining ($4000) in a 5.75% interest account, he will earn:
![A_2=4000(1+0.0575*1)=4230.](https://img.qammunity.org/2023/formulas/mathematics/college/k2qaqgxbj5tzx7fkpoh3alihtid5neee76.png)
Then, after one year he will have a total of $4230+$1055=$5285, therefore he will gain $285.
Answer: $285.