A soft-drink vending machine is supposed to pour 500ml of the drink
into a bottle. However, the actual amount poured into a bottle varies.
The amount poured into a bottle follows a normal distribution with a
mean that can be set to any desired amount by adjusting the machine.
The standard deviation of the amount poured is always 0.10ml
regardless of the mean amount. If the owner of the machine wants to
be 95% sure that the amount in each bottle is 8ml or more, to what
level should she set the mean?​