Interior decorator: All coffeehouses and restaurants are public places. Most well–designed public places feature artw...

Mehran on August 27, 2018

Hi @RJEh, thanks for your post. Let's examine the stimulus first. This one does not present an argument. Rather, it puts forward a set of facts, each of which you could diagram.

(1) All coffeehouses (C) and restaurants (R) are public places (PP). C and R ==> PP
(2) Most well-designed public places (WDPP) feature artwork (FA). WDPP-most-FA
(3) If a public place is uncomfortable (U) it is not well designed (not WD). U==>not WD. Contrapositive: WD ==> Comf (not uncomfortable = comfortable)
(4) All comfortable (C) public places have spacious interiors (SI). Comf ==> SI

Answer choice (D) says "Any well-designed coffeehouse or restaurant (WD) has a spacious interior (SI)."
Yes, this must be true. First, the first premise tells you that coffeehouses and restaurants are public places. This means that the 2nd, 3rd, and 4th claims in the stimulus - which are about public places - apply to coffeehouses and restaurants.

Next, combine the contrapositive of the 3rd statement (WD ==> Comf) with the 4th statemnet (Comf ==> SI) for the following transitive:
WD ==> Comf ==> SI (if well-designed public place, comfortable; if comfortable public place, then spacious interior).

Hope this helps! Please let us know if you have any additional questions.