The article “mix design for optimal strength development of fly ash concrete” (cement and concrete research, 1989, vol. 19, no. 4, pp. 634–640) investigates the compressive strength of concrete when mixed with fly ash (a mixture of silica, alumina, iron, magnesium oxide, and other ingredients). the compressive strength for nine samples in dry conditions on the twenty-eighth day are as follows (in megapascals): 40.2 30.4 28.9 30.5 22.4 25.8 18.4 14.2 15.3 find a 95% prediction interval on the next sample that will be tested. assume population is approximately normally distributed. round your answers to 2 decimal places.