12. A mall

sells a product, and due to
the purchase price being reduced by
$6.4 \%$ compared to the original
purchase price, the profit margin increased by 8 percentage points. Therefore, the original profit margin for selling this product is $\qquad$ . (Profit margin $=$ $\frac{\text { selling price - purchase price }}{\text { purchase price }} \times 100 \%$ )
$12.17 \%$