A department store is having a sale. The advertising hoarding for the sale is shown
below:
30% off if the marked prices
total more than $100.
If you buy three items, you
get the least expensive free.
This is a bit ambiguous. I don’t know
whether they give me the free item before
they calculate whether it is over $100, or
after. Suppose I buy three items at marked
prices of $40, $40 and $30. What could I
expect to pay under either interpretation?