Hi,
I have taken the following approach to solve this question. Please correct me if I am wrong.
Let H = No. of Hardback version books
P = No. of Paperback version books
h = SP(Sales Price) of one hardback version book
p = SP(Sales Price) of one paperback version book
Total no. of books sold out => H + P = 1200 (Given)
h = 2p (Given)
Statement 1:-
h + p =$60
2p + p = $60
p = $20
therefore h = 2p = $40
But we don't have any information about the total cost for purchasing 1200 books because we don't know the total count of each type of book.
So. this statement is insufficient. We can eliminate options A and D.
Statement 2:-
Total Revenue from the sales of the books is $30,00 i.e
hH + pP = 30,000
Here, we don't know the values of h and p, so we cannot solve this equation.
So this statement is insufficient. We can eliminate option B.
Considering both statements together,
h=$40, p=$20
So substituting these values in the above equation,
40H + 20P=30,000
H + P =1200 (Given in the question)
We have 2 variables and 2 equations, so we can solve for the 2 variables(H & P).
So both statements together are sufficient.
Option C is the answer.