Final answer:
If the author had hired someone to type the manuscript, the GDP would have been higher.
Step-by-step explanation:
If the author had hired someone to type the manuscript, it would have affected the Gross Domestic Product (GDP) by increasing it. Hiring someone to type the manuscript would have created a job and generated income for the typist. This additional income would have been included in the GDP calculation as part of the country's economic activity.
Keynes argued that the level of GDP in the economy is not primarily determined by the potential of what the economy could supply, but rather by the amount of total demand. In this case, hiring someone to type the manuscript would have increased the demand for labor and contributed to economic growth, leading to a higher GDP.
In summary, if the author had hired someone to type the manuscript, the answer is a) GDP would have been higher.