Hi Neilsheth2,

We're given the formula C(X) = 10,000 + BX + AX^2, where A and B are constants, C is the 'cost' and X is the number of units. We're asked for the value of A.

1) 500 units cost $15,833

Using this information, we can plug in these values to the given equation...

15,833 = 10,000 + B(500) + A(500^2)
5,833 = 500B + 2500A

This is one equation with two variables. There are multiple possible values for A.
Fact 1 is INSUFFICIENT

2) 1000 units costs TWICE what 500 units cost.

Using this information, we can create the following big equation.

[10,000 + B(1000) + A(1000^2)] = 2[10,000 + B(500) + A(500^2]

Now we can simplify and combine like terms:

10,000 + 1000B + 1,000,000A = 20,000 + 1000B + 500000A
500,000A = 10,000
A = 10,000/500,000
A = 1/50
Fact 2 is SUFFICIENT

Final Answer: B

GMAT assassins aren't born, they're made,
Rich