17 Develop the activity sequence model and determine the normal time for the following work activity: A worker picks up a screwdriver within reach from his worktable positions it onto the head of a screw, fastens the screw with 6 turns, and lays the serewdriver aside. 18 Develop the activity sequence model and determine the normal time for the following work activity: An assembly worker on a production line obtains an Allen key within reach, positions it 15 cm (6 in.) onto a bolt head, cranks it times to seat the bolt, and then sets the key aside. 19 Express the MTM-1 motion elements in Problem 8 as one or more MOST activity sequence models with index numbers. (a) Determine the normal times in TMUs for these activity sequence models. (b) What is the total time for this these) activity sequence model(s) in sec- onds? (c) How do the MOST normal times compare with the normal times from MTM-I? 20 Express the MTM-1 motion elements in Problem 9 as one or more MOST activity sequence models with index numbers. (a) Determine the normal times in TMUs for these