In order to get Kittyville's GDP to the full-employment GDP, the increase in government spending should be $20 billion.
The amount the government should increase its spending by is:
= GDP gap / Multiplier
Multiplier = 1 / ( 1 - MPC)
= 1 / ( 1 - 0.9)
= 10
Amount to increase spending by:
= (600 - 400) / 10
= 200 / 10
= $20 billion
In conclusion, government spending should increase by $20 billion.
Find out more on the spending multiplier at https://brainly.com/question/490794.