Given: Cost of entrance for member = $8, cost of entrance for visitor = $12
Average cost of all the tickets sold =?

Let x = number of members, y = number of visitors, and Total revenue = T
Also, T = 8 * x + 12 * y
Average cost = Total revenue/Total of visitors and members entered = \(\frac{T}{x + y}\) =?

Statement 1:
T = $620
There is no data on x and y.
Statement 1 is Not Sufficient.

Statement 2:
x : y = 4 : 7
=> x = \(\frac{4y}{7}\)
There is no information on total revenue.
Statement 2 is also Not Sufficient.

Statement 1 and Statement 2 combined:
T =$620 and x = \(\frac{4y}{7}\)
Also, T = 8x + 12y
Average = \(\frac{T}{x + y}\) = \(\frac{8x + 12y}{x + y}\) = \(\frac{8(x + y)}{x + y}\) + \(\frac{4y}{x + y}\) = 8 + 4 * \(\frac{7}{11}\) \(\approx\) 8.5 [\(\frac{y}{x + y}\) = \(\frac{7}{11}\)
Statement 1 and Statement 2 together are Sufficient.

So, correct answer is option C.


P.S. - If we try to solve the equations, we get x = 21.38 and y = 37.41, which is not possible, as number of visitors and members have to be whole numbers.
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