If all quantities produced rise by 10 percent, and all prices fall by 10 percent, which of the following occurs? I am having a hard time deciding for this question:

If all quantities produced rise by 10 percent, and all prices fall by 10 percent, which of the following occurs?

A) Real GDP rises by 10 percent, while nominal GDP falls by 10 percent.

B) Real GDP rises by 10 percent, while nominal GDP is unchanged.

C) Real GDP is unchanged, while nominal GDP rises by 10 percent.

D) Real GDP is unchanged, while nominal GDP falls by 10 percent.

I think it is either A or B, because I know that real GDP rises but i'm not sure what happens to the nominal GDP. if anyone can help, it would be much appreciated.
It helps to write out things as (simple but) proper equations. Denote production as $Y$ and prices as $P$

It is given that

$$Y_{t+1} = 1.1 Y_t \\
P_{t+1} = 0.9 P_t$$

Nominal GDP is given by $P_t Y_t$

$$ P_{t+1}Y_{t+1} = 1.1 Y_t \cdot 0.9 P_t  \\
= 1.1\cdot 0.9 \cdot Y_t P_t$$

So nominal GDP changed by $1.1 \cdot 0.9 = 0.99$ - it dropped by one percent. 

So which answer is it?

I assumed that the initial value is base value for the description of the relative changes. If, instead, we have that the larger value is base for the relative change, 

$$0.9 Y_{t+1} = Y_t \\
P_{t+1} = 0.9 P_t$$

we get that 
$$ P_{t+1}Y_{t+1} = \frac{1}{0.9} Y_t \cdot 0.9 P_t = Y_t P_t  $$


nominal GDP does not change.