To calculate the interest earned in one year with a simple interest rate, you can use the formula:
\[ \text{Interest} = \text{Principal} \times \text{Rate} \times \text{Time} \]
In this case:
- Principal = $40
- Rate = 10% = 0.10
- Time = 1 year
Now, plug in the values:
\[ \text{Interest} = 40 \times 0.10 \times 1 = 4 \]
So, the interest earned during any one of the years the money is deposited is:
\[ \boxed{4} \]