Solve the Problem $t$ Is Given By $s ( t )$ Find the Instantaneous Velocity at the Indicated Value Of t

Solve the problem.
-The position of an object at time $t$ is given by $s ( t )$ . Find the instantaneous velocity at the indicated value of $t$ . $s ( t ) = \frac { 3 } { t - 1 } \quad$ at $t = 4$

A) $- 1$
B) $- \frac { 1 } { 3 }$
C) $- 3$
D) 1