Students in a fifth-grade class were given an exam. During the next \( 2 \) years, the same students were retested several times. The average score was given by the model
\( f ( t ) = 93 - 12 \log ( t + 1 ) , 0 \leq t \leq 24 \)
where \( t \) is the time in months. Round answers to at least \( 1 \) decimal point.