If MPS=0.2, then
MPC= 1-MPS= 1-0.2 = 0.8
Consumption Function is C = c + 0.8 Y where Y in the income in the economy and c= Autonomous consumption.
At equilibrium level of output,
AS=AD
Y= C+I
=> 1,250 = c + 0.8 (1,250) + 150
=> 1,250 = c+ 1,000 + 150
=> 1,250 = c+ 1,150
=> c = 1,250- 1,150 = 100.