Suppose the consumption function is C = $500 billion + 0.9Y and the government wants to stimulate

Question:

Suppose the consumption function is C = $500 billion + 0.9Y and the government wants to stimulate the economy. By how much will aggregate demand at current prices shift initially (before multiplier effects) with
(a) A $50 billion increase in government purchases?
(b) A $50 billion tax cuts?
(c) A $50 billion increase in income transfer?