The profit function P(x) will be zero when either of its factors is zero. The left factor (x-3) is zero when x=3. The right factor (x-11) is zero when x=11.
Prices of $3 or $11 will result in $0 annual profit.
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<em>Additional comment</em>
A price halfway between these values, at (3+11)/2 = 7, will produce maximum profit, $32 million.
Start from the last plane. Rachel's plane flew 20 ft. Darren's plane flew twice as far as Rachel's, so Darren's plane flew 2 * 20 ft = 40 ft. Amanda's plane flew 19 ft farther than Darren's, so Amanda's plane flew 40 ft + 19 ft = 59 ft.
