P, Q, R, S are four digit numbers, each having the digit 9 only once and in the place shown below. None of the other digits are known.What can be said about P, Q, R, S from the following?

Question

$\begin{array}{11} (a)\; \text{S is the smallest of the four numbers} \\ (b)\; \text{Q is larger than R} \\ (c)\; \text{P is the largest of four numbers} \\ (d)\; \text{S is the largest of the four numbers } \end{array}$