The mean bill per customer at Shane's Service Station is $9.50 with a standard deviation of $0.75. The median bill is $10.00. The mean amount of time spent by a customer in the station is 6.5 minutes with a standard deviation of 2 minutes.
According to Chebychev's Theorem, what proportion (percent) of the customers spent between 3.30 minutes and 9.70 minutes at the station?