What is the sum of all 4-digit numbers less than 2000 formed by the digits 1, 2, 3 and 4, where none of the digits is repeated?
A
7998
B
8028
C
8878
D
9238
Correct Answer: Option A
Explanation
1. **Analyze Constraints**: We need 4-digit numbers using {1, 2, 3, 4} without repetition, and they must be **less than 2000**.
2. **Fix the Constraint (Anchoring)**:
- To be