One can ask about the time until a child first asks ``Are we there yet?''. This is different from the time at which a child first asks. This is given by subtracting the current time from both sides of the previous equation. The result is
is the time from now until a child first asks ``Are we there yet?''
is the time since we left (the house)
C is the number of children in the car
A is the number of activities
and are parameters.