The polynomial P(x)=x^{3}+a x^{2}+b x+c has the property that the mean of its zeros, the product of its zeros, and the sum of its coefficients are all equal. If the y-intercept of the graph of y=P(x) is 2 , what is b ?
Answer Choices
A. -11
B. -10
C. -9
D. 1
E. 5