sigmaAllow = 15000 // psi
width = 11 // inch
p = 150 // Force on shelf - lbs
distance = 12 // inches
FOS = 2
thickness = sqrt(distance * p * FOS * 6 / (sigmaAllow * width))
filletR = thickness * 2
shelfMountL = 9
wallMountL = 8

bracket = startSketchAt([0, 0])
  |> line([0, wallMountL], %)
  |> tangentialArc({ radius: filletR, offset: 90 }, %)
  |> line([-shelfMountL, 0], %)
  |> line([0, -thickness], %)
  |> line([shelfMountL, 0], %)
  |> tangentialArc({
       radius: filletR - thickness,
       offset: -90
     }, %)
  |> line([0, -wallMountL], %)
  |> close(%)
  |> extrude(width, %)