The $x$ and $y$ coordinates of a particle at any time $t$ are given by $x=7 t+4 t^{2}$ and $y=5 t$, where $x$ and $y$ are in $\mathrm{m}$ and $t$ in
s. The acceleration of the particle at $5 \mathrm{~s}$ is
a. zero
b. $8 \mathrm{~m} / \mathrm{s}^{2}$
c. $20 \mathrm{~m} / \mathrm{s}^{2}$
d. $40 \mathrm{~m} / \mathrm{s}^{2}$