I'm reading 'Rational Points on Elliptic Curves'‘Rational Points on Elliptic Curves’ by Silverman and Tate, and the exercise 4.6 is about the following special case of Eichler-Shimurathe Eichler–Shimura theorem. Let $C$ be the elliptic curve given by the equation $C: y^2 = x^3-4x^2+16$ and let $F(q)$ be the formal power series given by the infinite product $F(q) = q \prod_{n=1}^\infty (1-q^n)^2(1-q^{11n})^2$. Let $N_n$ be the coefficient of $q^n$ in $F(q)$, so $F(q)=\sum_{n=1}^\infty N_n q^n$. The exercise is to prove that $M_p+N_p=p$, where $M_p$ is the number of points on $C$ over the field $\mathbb{F}_p$. So, what is the idea of proof? Because I have no ideas how $M_p$ and $N_p$ can be connected. Thanks in advance!