23) B

Probability of false positive on PSA = 0.1 x 0.74 = 0.074
Probability of false positive on DRE = (85 ÷ 1000) x 100 = 8.5% = 0.085

Probability of false positive on both = 0.074 x 0.085 = 0.00629

This gives us a percentage of 0.6% which is 6/100.
So B is the answer.

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