The extended demand function of good X is:

QDX = 1400 - 20 PX - 10 PY + 0.1 M where:

QDX = quantity demanded of good X

PX = Price of good X

PY = Price of related good Y (related in consumption to good X)

M = Average consumer income .

Assume the following

M = 10,000

PY = 50,

Assume the same extended demand function of good X as in the previous questions:

QDX = 1400 - 20 PX - 10 PY + 0.1 M

Assume that

PX= 50

M =10,000

PY starts at 50 and then increases to 80.What is thecross-price elasticity of the demand of good X when the price of good Y increases from 50 to 80.