Researchers fed cockroaches a sugar solution. Ten hours later, they dissected the cockroaches and measured the amount of sugar in various tissues. Here are the amounts (in micrograms) of d-glucose in the hindguts of 5 cockroaches:

55.95      68.24      52.73      21.50      23.78

(The standard deviation of this sample is 20.74.)

From previous work, the researchers expected the population of responses to be Normal. The insects are a random sample from a cockroach population grown in the laboratory. A 90% confidence interval for the mean amount of d-glucose in cockroach hindguts under these conditions is__________