How many 6-bit strings (that is, bit strings of length 6) are there which:
  1. Start with the sub-string 101?
  2. Have weight 5 (i.e., contain exactly five 1’s) and start with the sub-string 101?
  3. Either start with 101 or end with 11 (or both)?
  4. Have weight 5 and either start with 101 or end with 11?

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