Arrange the nine non-zero decimal digits in a certain order
e.g. abcdefghi.
Now evaluate abc*cba+def*fed+ghi*ihg
Call the result R and the number of distinct digits in it D(R).

Example: for concatenation 125736849 R=1339330 and D(R)=4

a, What concatenation, if any, results in D(R)=7?
b. For what concatenation(s) the D(R) is minimal?

Rem: Due to symmetry there will be multiple solutions, please list the lowest one only.