The average annual medical costs for a family of four in the United States from 2001 through 2011 is approximated by the function
$$
C(t)=22.9883 t^{2}+830.358 t+7513 \quad(1 \leq t \leq 11)
$$
where $t$ is measured in years, with $t=1$ corresponding to 2001 , and $C(t)$ is measured in dollars.
a. What was the approximate average annual medical costs for a family of four in $2010 ?$
b. How fast was the approximate average medical costs for a family of four increasing in $2010 ?$