A blanking disk is 20 mm thick and is to be fastened to a spool whose flange is 25 mm thick, using eight M12 x 40 hex-head metric cap screws. 1) What is the length of the threads LT for this fastener? 2) What is the effective grip length /? 3) Is the length of this fastener sufficient? If not, round to the next preferred length. 4) Find the shank length ld and the useful threaded length in the grip Ir. These lengths are needed in order to estimate the fastener spring rate kb.