$4-1.$ Select the lightest W$10$ section available to support working tensile loads of

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$=$

$120$

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and

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$=$

$160$

$$k

$.$

The member is to be $18$ ft long and is assumed to have two lines of holes for

$3/4$

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bolts in each flange. There will be at least three holes in each line $3$ in on center.