Answer
a)0.012.
b)It is not worth playing.
Work Step by Step
a) The expected value: $1,000,000\cdot \frac{1}{90,000,000}+100,000\cdot \frac{1}{110,000,000}+25,000\cdot \frac{1}{110,000,000}+5,000\cdot \frac{1}{36,667,000}+2,500\cdot \frac{1}{27,500,000}=0.012$
b)The expected value is a lot less than the cost of a stamp, therefore it is not worth playing.