Probability Help!!!!!!!!!!!!!!!!!!!!!!!!

From a box containing five white balls and four red balls, two balls are selected at random without replacement. Find the probabilities of the following events:
a. exactly one white ball is selected
b. at least one white ball is selected
c. two white balls are selected, given that at least one white ball is selected
d. the second ball drawn is white

a. P = P(WB) + P(BW) = 5/9*4/8 + 4/9*5/8 = 40/72 = 5/9

b. P = 1 - P(BB) = 1 - (4/9*3/8) = 12/72 = 1/6

c. All possible outcomes:
WW, BW, BB, WB
P(WW) = 5/9*4/8 = 20/72 = 5/18
P(BW) = 4/9*5/8 = 20/72 = 5/18
P(BB) = 4/9*3/8 = 12/72 = 1/6
P(WB) = 5/9*4/8 = 20/72 = 5/18
P = P(WW) / [P(BW) + P(WB) + P(WW)] = 1/3

d. P = P(W2 given B1) + P(W2 given W1) = 4/9*5/8 + 5/9*4/8 = 5/9