The demand for good X

The demand for good X has been estimated to be ln Qxd = 100 – 4.2 ln PX + 5.5 ln PY + ln M. The own price elasticity of good X is:

a)− 4.2.

b) 4.2.

c)− 5.5.

d) There is insufficient information needed to find the elasticity of good X.

I need assistance with the above question.  Please show the work as to how you came up with one of the 4 answers above. Need by 6 pm today.