The effect on real GDP of a $175 billion in the case when there is a change in the planned investment should be $350 billion.
As we know that
Multiplier = 1 ÷ (1 - MPC)
= 1 ÷ 1-0.50
= 2
Now
Change in GDP = Multiplier × Change in investment
= 2 × 175
= $350 billion
Therefore for computing the Change in GDP we simply applied the above formula i.e of Multiplier and the change in gross domestic product (GDP)
Hence, The effect on real GDP of a $175 billion in the case when there is a change in the planned investment should be $350 billion.
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