ive been reading a bit about bayes theorem and the answer to this question has me confused

question:

Two video products distributors supply video tape boxes to

a video production company.Company Asold100 boxesof which5were

defective.Company Bsold300 boxesof which21were defective. If a box

was defective, .find the probability that it came fromCompany B.

The answer given is

0:192

has the author of the question calculated that the defective box came from

company Anot company b

so the answer should be0.8076

or have i missed something here?