You collected a random sample from an underlying random variable, and with that sample you calculated/constructed a 95% confidence interval ("95% C.I.") for the population mean of the underlying random variable. The 95% C.I. that you constructed is:

95% C.I.: (100 , 150)

Based on this result, please calculate/construct a 81% confidence interval for the population mean of the underlying random variable (under the assumption that you would be using the same sample of data that you used to construct the above 95% C.I.).