OS 28 29 30 31 31 1/2 32 32 1/2 33 34 34 1/2 35 36 1/2 36 2/3 37 1/3 37 1/2 38 38 1/2 38 2/3 39 39 1/3 40 30-31 32-33 33-34 34-35 36-37 37-38 38-39