A box contains 6 red and 4 blue marbles. Two marbles are drawn successively.
Situation I: The first marble is replaced before drawing the second.
Situation II: The first marble is not replaced.
If P1 is the probability of getting two red marbles in Situation I and P2 is the probability of getting two red marbles in Situation II, what is the ratio P1:P2?
a) 27:20
b) 27:25
c) 25:27
d) 6:5