If the mpc is 9 initial GDP is 800 billion government spending falls by 5 billion what is the new level of GDP?

If the mpc is 9 initial GDP is 800 billion government spending falls by 5 billion what is the new level of GDP?
change in y/ change in g = 1/1-mpc... x/5bill= 10 so x= 50bill new level of GDP = 850bill