A snail, an ant, and a beetle are having a race. The course is a straight line from position p subscript s equals open square brackets table row 2 row 0 row 3 end table close square brackets to position p subscript f equals open square brackets table row 6 row 0 row cell negative 5 end cell end table close square brackets. The snail finishes the race in 4 seconds. Write down the parametric equation for the snail's position as a function of time, S left parenthesis t right parenthesis, assuming that the race starts at time t equals 0.