A timber company wishes to increases sales of timber by supplying log cabin kits that can be assemed and used as vacation cabins. As the structural engineering for the company you must (a) determine an expression that relates the maximum shear stress in a log (circular cross section) to the transverse shear force V and the diameter d and (b) determine the maximum span, Lmax, of a simply supported log beam that must support a uniformly distributed load w (including beam weight) without exceeding the allowable shear stress, Tallow.