There are numerous standards for paper sizes around the world. Three particularly important paper sizes are: Letter, measuring 216 mm 279 mm; Legal, measuring 216 mm 356 mm; and A4, measuring 210 mm 297 mm. In addition, any piece of paper may be used in portrait mode (with the long edge oriented vertically), or in landscape mode (with the long edge oriented horizontally).

Write a function page-width that consumes two symbols. The first symbol, size, is one of 'letter, 'legal, or 'A4. The second symbol, orientation, is one of 'portrait or 'landscape. The function produces a number, giving the horizontal extent in millimeters of a piece of paper of the given size and in the given orientation. For example (page-width 'letter 'portrait) 216, and (page-width 'A4 'landscape) 297.

(Use Racket language)