SAE 10W-30 oil with viscosity 1 × 10^–4 lbf∙s/ft² is used as a lubricant between two parts of a machine that slide past one another with a velocity difference of 4 ft/s. What spacing, in inches, is required if you don’t want a shear stress of more than 2 lbf/ft²? Assume Coquette flow.