Beer & Johnston — Stress and Strain—Axial Loading: Problem 2.13

2.13 Rod $BD$ is made of steel ($E = 29 \times 10^6$ psi) and is used to brace the axially compressed member $ABC$. The maximum force that can be developed in member $BD$ is $0.02P$. If the stress must not exceed $18$ ksi and the maximum change in length of $BD$ must not exceed $0.001$ times the length of $ABC$, determine the smallest-diameter rod that can be used for member $BD$.