Answer: b. left by about $26.7 billion.
Step-by-step explanation:
The multiplier determines how much government spending affects the aggregagte demand.
Multiplier is:
= 1 / ( 1 - MPC)
= 1 / (1 - 0.625)
= 2.67
The effect on Aggregate demand is:
= Government spending * Multiplier
= -10 billion * 2.67
= -$26.7 billion
Aggregate demand will shift left by $26.7 billion to show that aggregate demand is decreasing.