Answer:
B. S and I drop by $0.60 trillion. 
Step-by-step explanation:
We know that 
Y = C + I + G 
$12 trillion = $8 trillion + I + $2 trillion 
$12 trillion = $10 trillion + I 
So, I = $12 trillion - $10 trillion 
 = $2 trillion 
As the government purchases increase from $2 trillion to $2.60 trillion 
and the rest of the things remain the same. 
So New I = $12 trillion - $8 trillion - $2.60 trillion 
 = $1.4 trillion 
So, the difference would be equals to 
= $2 trillion - $1.4 trillion 
= $0.6 trillion 
The $0.6 trillion reflect fall in the investment 
And the saving and the investment are equal to each other 
Hence, the B option is the right answer