How do trade-offs and opportunity costs relate to making personal economic decisions?

Tanya was used to using word, and she did some work for her brother mike, who was using wordperfect. tanya was quickly able to use wordperfect for windows with little difficulty, since many of the commands for it were the same as the commands for word. tanya's ability to use wordperfect best illustrates:

What service name do you like? 1.schoolbrella 2.schoolplicity 3.studentaxle 4.studiley 5.edulliance 6.savantsnap 7.peaklemon 8.swiftgrasp 9.educaco 10.vistarise 11.iqpursuit 12.studentpivot 13.edgyadvice 14.studenterra

Using mr smith and his id, identify two potential internal validity threats that might affect the a—b design. tell me how that threat might impact conclusions in the a—b design. note #1: you cannot use maturation (since i already did that one for note #2: there are some mr smith id threats that won’t have much impact in a single case design.