First premise. I denoted it as, P-->Q. "If price it pays for coffee beans increase then the shop will increase its price"
Second premise denoted as, Q-->(R v S).
"In case Q---the shop increasing its price----, then either R---shop will begin selling non-coffee products---or S--coffee sales will decrease."
Third premise. R-->T. "If shop sells non-coffee products then overall profitability will decrease."
Fourth premise. ~T-->~S. "shop can avoid decreasing profit only if its coffee sales do not decrease."
the ~ denotes a negation and key word, "only if" is the consequent of a conditional.
Just a quick recap on conditionals: there are 2 components, the antecedent and the consequent.
the antecedent of a conditional is the "if" part of a conditional statement for example, "IF I go for a walk today, THEN it is sunny"
and the term, "only if" is equivalent to "then" thus, the fourth premise is symbolically denoted as ~T-->~S.
Now let's take a look at each conclusion and see which ones are valid.
A) If overall profitability decreases, the price it pays for coffee beans will have continued to increase.
This is symbolically equivalent to "If T then P".
Right away I can tell this is incorrect based on truth tables for conditional logic.
P --> Q
T T T
T F F
F T T
F T F
So the T's and F's represent true or false; it is binary and for a conditional, there are 4 total possible combinations of the validity for statement P and statement Q.
I will not go into detail on truth tables, you can wikipedia it yourself to follow along.
We see that in a conditional, there is only one instance that would make a conditional statement false, which is when the antecedent is true and the consequent
is false.
It basically means that when you have a conditional if the antecedent is true, then the consequent must necessarily follow.
However, we see that the consequent can be True even if the antecedent is false.
Where validity of P is False and validity for Q is true.
Now for conclusion A, we see that in order for T--"profit decrease" to even be valid, it requires the antecedent R---sells noncoffee products. And R requires the antecedent Q---increase sale of coffee beans.
Q. Q ---> (R v S). R-->T.
And as we've seen, Q can occur even if P does not occur, so P---price it pays for coffee beans increase---can never be contingent on T---profit decrease.
For conclusin B) If the shops overall profitability decreases, either it will have begun selling non-coffee products or its cotton sales will have decreased.
T --> (R v S).
here we have the same problem as A. the antecedent and consequents are flipped and they are not equivalent. the only way a conditional is equal both ways is if it is a bi-conditional, the key term for bi-conditional is "if and only if"
conclusion C) the shops overall profit will decrease if the price it pays for coffee beans continues to increase.
P --> T.
Another way to word the conclusion is, "if the price it pays for coffee beans continue to increase, the shops overall profit will decrease".
So here, I will show you what is called a derivation. Basically its like accounting but for arguments.
Premises: P--->Q. Q-->(R v S). R-->T. ~T-->~S.
Conclusion: P-->T
[align=]
1) Prove P-->T -----------------> line 3, conditional proof
2) P Assume the conditional
3) Prove T -----------------> line 9, direct proof
4) ~T Assume the indirect
5) ~S line 4, Premise 4. Modus Ponens
6) Q line 2, Premise 1. Modus Ponens
7) R v S line 6, Premise 2. Modus Ponens
8) R line 5, line 7, Modus Tollendo Ponens (disjunctive syllogism)
9) T line 8, Premise 3. Modus Ponens
[/align]
Now on line 3 we can provide our reasoning which is a direct proof of the consequent T.
And finally, for line 1, we proved the conditional P-->T
logically speaking, conclusion C is valid, given the premises, therefore C is the correct answer.
Edit:
Sorry I do not know how to align properly in this text editor. i will post a screenshot of the derivation using a logic software.