Solve each problem.
Sales (in thousands of units) of a new product are approximated by the logarithmic function
$$
S(t)=100+30 \log _{3}(2 t+1)
$$
where $t$ is the number of years after the product is introduced.
(a) What were the sales, to the nearest unit, after 1 yr?
(b) What were the sales, to the nearest unit, after 13 yr?
(c) Graph $y=S(t)$