It seems you uploaded a document containing several digital electronics-related questions. Here's a breakdown of the questions from your document:

1. Convert the following decimal numbers to BCD 8421:

   • a. 8531 (10)
   • b. 4725 (10)

2. Perform the following decimal additions in BCD:

   • a. 735 + 328
   • b. 5421 + 482
   • c. 2475 + 3284

3. Design a BCD to 7-segment decoder circuit:

   • a. Decoder BCD to 7-segment, segment A
   • b. Decoder BCD to 7-segment, segment D
   • c. Decoder BCD to 7-segment, segment G

4. Design a 4x1 Multiplexer circuit.

5. From the given 4-channel DE-MUX diagram, create a truth table.

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