Given below are two quantities named I and II. Based on the given information, you have to determine the relation between the two quantities. You should use the given data and your knowledge of Mathematics to choose among the possible answers.

Two trains C and D each having length of 100 metres are moving in the opposite direction. Both trains cross each other in 10 seconds. If train C crosses a 200-metre long platform in 30 seconds.

Quantity I: Find the speed of train D.

Quantity II: Find the speed of train C, if train C crosses a 100 metres long platform in 25 seconds.