The length of licorice sticks is found to be normally distributed with a mean length of 15.6 cm and a standard deviation of 0.24. In a batch of eight such sticks, what is the probability that six of them will be between 15cm and 16cm?

My approach was using normalcdf(15,16,15.6,0.24), but this did not result in the correct answer. Can anyone help me with this problem? Thank you very much.