Contrapositive of the statement :

(1) If a function $f$ is continuous at $a$, then it is not differentiable at $a$.

(2) If a function $f$ is not continuous at $a$, then it is not differentiable at $a$.

(3) If a function $f$ is not continuous at $a$, then it is differentiable at $a$

(4) If a function $f$ is continuous at $a$, then it is differentiable at $a$.