In the equation SEND + MORE MONEY, each letter represents a different digit (0–9). The addition is..

In the equation SEND + MORE MONEY, each letter represents a
different digit (0–9). The addition is done in the usual way from right to
left, first adding D and E to obtain Y (possibly with a carry-over), then
adding N and R, and so on. Develop a linear integer model to determine the
digit represented by each letter.