Consider the following BNF grammar that describes

some of the "technical elective" courses allowed by the CS degree

plan.

->

-> |

-> |

-> CS4330 | CS4317 | CS4339 | CS4381

-> CS4390 | CS4371 | CS4373

You need to take at least five technical elective courses. However,

no more than two courses of CS4390 (Special Topics), CS4371

(Independent Studies) and CS4373 (Internship) in any combination

can count for technical electives.

CS4390 CS4330 CS4317 CS4339 CS4381 -- ok: one special course

CS4390 CS4390 CS4317 CS4339 CS4381 -- ok: two

CS4390 CS4371 CS4317 CS4339 CS4381 -- ok: two

CS4390 CS4390 CS4390 CS4330 CS4317 CS4339 -- ok: why?

CS4390 CS4330 CS4317 -- not okay: < five

CS4390 CS4390 CS4373 CS4330 CS4342 -- not okay: three

Extend the given BNF grammar to an attribute grammar to

specify the above rules.