15. The teacher asked the students to calculate $\overline{A B} . C+D . E$. Ma Xiaohu missed the decimal point in $D . E$, getting the wrong result of 39.6; while Ma Dahu mistook the plus sign for a multiplication sign, getting the wrong result of 36.9. What, then, should the correct calculation result be?
【Analysis】From the calculation result of Xiaohu Ma, we know that $\mathrm{C}$ is 6.
Considering the calculation result of Dahu Ma, there is one decimal place in each number in the original expression, so the product should have 2 decimal places. However, the final result has only one decimal place, so the omitted one must be 0. Therefore, $\mathrm{E}$ is 0 or 5.
If $\mathrm{E}$ is 0, then Dahu Ma calculated $\overline{A B} . C \times D$, and $\mathrm{C}$ is 6, which is an even number, so the last digit of the result should be an even number, but the result is 9, which is odd, so $\mathrm{E}$ is 5.
Thus, the original expression is $\overline{A B} .6+D .5$.
From the calculation result of Xiaohu Ma, we know that $\mathrm{B}$ is 4, and $\mathrm{A}+\mathrm{D}$ is 3.
Note that here D can be 0.
Verify sequentially, $34.6 \times 0.5=17.3, 24.6 \times 1.5=36.9, 14.6 \times 2.5=36.5$,
We can see that the correct calculation result is $24.6+1.5=26.1$.