A local gas station waits 4 days to receive its delivery after he calls and places an order. The amount of gas that the station sells in a day is independent of other days and follows a Normal distribution with mean 1000 gallons and standard deviation of 400 gallons. Which one of the statements is true?
a. The chance of selling more than 1400 is around 15%
b. The chance of selling more than 1400 is around 5%
c. The chance of selling more than 1400 is zero
d. The chance of selling more than 1400 is around 10%