If the five-year-old's mental age is also five, and the 60-year-old's mental age is 60, then they both have an IQ of 100: 5/5 x 100 = 100 (average IQ - on age level).
Booth was shot dead in a firefight with Union cavalry troops in a barn in the Virginia countryside on 26th April 1865, after having been on the run for 10 days.
There was certainly nothing Lincoln could do on the evening of April 14, 1865 when John Wilkes Booth entered the presidential box at Ford's Theatre. The stage actor fatally shot Lincoln in the back of the head, triggering a manhunt for the murderer and his conspirators and a long period of national mourning.