Four friends have been identified as suspects for an authorized access into a computer system. They have made statements to the investigating authorities. Alice said "Carlos did it." John said "I did not do it." Carlos said "Diana did it." Diana said "Carlos lied when he said I did it"


(a) If the authorities also know that exactly one of the four suspects is telling the truth, who did it? Explain your reasoning.
(b) If the authorities also know that exactly one of them is lying, who did it? Explain your reasoning.

There must be a price
for brain racking!

Alice was saying the truth.
Her allegation wasnt denied,
and no one accused her.

John wasnt accused also.
Instead, he exonerated
himself.

Carlos did it.
He shifted the blame to Diana
after being unrefutably accused
by Alice.
Check out Diana's reply....

Carlos and Diana must have done it,
just like Alice and John were innocent.