The manager of Stetson and Stetson Company is trying to develop a time standard for the powder filling and packing operation. This operation has five work elements, each of which is performed once every cycle. The allowance for each work element is 18 percent. The operation was studied for 20 cycles, and the following summary data were obtained: 

a. Determine the standard time for the filling and packing operation. Assume the rating factor = 1.0.
b. Determine the sample size necessary if the estimate of the select time for the work elements is to be within ±3 percent of the true mean 95 percent of the time.

c. Is the sample size chosen to determine the standard time adequate? If not, how many additional cycles should be observed?