Bugfix:  Misc science, 50 metal, not 5000

Was fixed before but probably a bad mapmerge removed it.
Typo fix:  corpotate -> corporate.

And superfluous U removal 'MURIKA!
Merge pull request #4370 from Ccomp5950/metal_fix

Bugfix:  Misc science, 50 metal, not 5000
Merge pull request #4371 from Ccomp5950/typo_fix

america is dumb though
Merge pull request #4372 from Segrain/master

Small fixes.