Blood potassium level, continued. judy’s measured potassium level varies according to the normal distribution with with μ=3.8 and σ=0.2mmol/l. let’s consider what could happen if we took 4 separate measurements from judy. what is the blood potassium level l such that the probability is only 0.05 that the average of 4 measurements is less than l? (hint: this requires a backward normal calculation.)

the book says about 3.64 but i got 3.28