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Required information

The solid spindle $AB$ is made of a steel with an allowable shearing stress of $12$ ksi $,$ and sleeve $CD$ is made of a brass with an allowable shearing stress of $7\mathrm{.}6$ ksi $.$

NOTE: This is a multi$-$part question. Once an answer is submitted, you will be unable to return to this part.

Determine the corresponding required value of the diameter $d_S$ of spindle $AB.$

The corresponding required value of the diameter is $$ in$.$