Answer:
D
Step-by-step explanation:
The smallest possible allowable length that can be used:
Calculate area of contact between plates A
A = 2 * 6 * a
A = 12a in^2
Where a is an arbitrary constant length along the direction L.
Shear stress = Shear force / Area
Area = 15000 lb / 120 psi = 12*a
Evaluate a
a = 10.411 in
Total Length = 2*a + gap = 2*10.411 + 0.5 = 21.33 in
Answer: L = 21.33