Prob (A) = stop at 1st light = .4

Prob (B) = stop at 2nd light = .3

Prob (A and B) = .15

Whats the probability of stopping at just one light?

.4 x.7 + .6 x .3 = .46 but a Venn tells me it's .4

Probability of stopping at only first light?

.4 x .7 = .28 but a venn tells me it's .25

I know this has to do with the fact that they aren't independent events. I believe the correct answers are .46 and .25. Why use the venn in one and not the other?

Thanks!