GAUSS8 2000 Problem 4

Past Contests GAUSS8 GAUSS (GR. 8) - 2000
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1

In the addition shown, a digit, either the same or different, can be placed in each of the two boxes. What is the sum of the two missing digits?
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Answer Choices
A. 9
B. 11
C. 13
D. 3
E. 7