A large on-demand, video streaming company is designing a large-scale survey to determine the mean amount of time corporate executives watch on-demand television. A small pilot survey of 10 executives indicated that the mean time per week is 18 hours, with a standard deviation of 5.0 hours. The estimate of the mean viewing time should be within one-quarter hour. The 95% level of confidence is to be used. (Use z Distribution Table.)

How many executives should be surveyed? (Round the z score to 2 decimal places and final answer to the next whole number.)