The effectiveness of a blood-pressure drug is being investigated. An experimenter finds that, on average, the reduction in systolic blood pressure is 48.7 for a sample of size 981 and standard deviation 17.6. Estimate how much the drug will lower a typical patient's systolic blood pressure (using a 80% confidence level). Enter your answer as a tri-linear inequality accurate to one decimal place (because the sample statistics are reported accurate to one decimal place).