If the simple interest on Rs. `p` is Rs. `q` and simple interest on Rs. `q` is Rs. `r` (both time and annual simple interest rate are equal), which of the following relations is correct?<br />
(a) `pqr=1`, (b) `p^2 = qr`, (c) `q^2 = pr`, (d) `r^2 = pq`