Determine Whether the Following Symbolized Argument Is Valid or Invalid $\rarr$

Short Answer

Determine whether the following symbolized argument is valid or invalid.If invalid,provide a counterexample;if valid,construct a deduction.
P $\rarr$ Q
Q $\rarr$ R
R $\rarr$ S
(P $\rarr$ S) $\rarr$ (Q $\rarr$ ~P)
~P/ $\therefore$ ~Q