Can you please explain how the expert got this. Step by step

2. A taxi involved in a night-time hit-and-run accident was identified by an eyewitness as being blue. Suppose that in the city, 85% of the cabs are blue and 15% are green. Tests indicated that the witness (in conditions of poor lighting) was able to distinguish correctly the colors blue and green 80% of time. What is the probability that the cab was indeed blue given the eyewitness testimony? Car Color Witness Report P(BlWB) = 0.68 True Positive P(B) = 0.85 P(BlWG) = 0.17 P(GIWB) = 0.03 False Positive P(G) =0.15 P(GlWG)= 0.12 P(Blue CablSaw Blue) = .68!(.68+.03) = 0.95774