A state-of-the-art npn si transistor has a signal

Question

A state-of-the-art n/p/n Si transistor has a signal amplifying or electrically active p-type base layer whose volume is 1μm³ and which is doped with 10¹⁸ boron/cm³.

Suppose that the transistor will not work due to short-circuit paths in the base layer if the boron concentration In the p-base dropped below 10¹⁷cm^-3.

How many transistors must one fabricate to assure 100 good transistors? This is a real world problem.