50 . after the second world war claims of national interest have been used to support uneconomic or alling industries in some areas to the detriment of otherwise viable activities in other. (найти predicate , infinitive, function)

Have been used - сказуемое;
to support - инфинитив, в предложении выступает в роли обстоятельства цели (adverbal modifier of purpose).

Have been used- страдательный залог