Final answer:
To form the greatest product, we need to place the greatest digits in the positions of highest value. The substitutions would be A = 8, B = 6, C = 4, and D = 2.
Step-by-step explanation:
To form the greatest product, we need to place the greatest digits in the positions of highest value. Since the greatest value should be in the thousands position, we can place the digit 8 in the A position. For the next highest value, which should be in the hundreds position, we can place the digit 6 in the B position. For the tens position, we can place the digit 4 in the C position. And finally, for the ones position, we can place the digit 2 in the D position. So, the substitutions would be A = 8, B = 6, C = 4, and D = 2. This arrangement would form the greatest possible product.