Daily oil imports to the United States from Mexico can be approximated by
$$
I(t)=-0.015 t^{2}+0.1 t+1.4
$$
million barrels $/$ day $(0 \leq t \leq 8)$ where $t$ is time in years since the start of $2000 .^{2}$ According to the model, in what year were oil imports to the United States greatest? How many barrels per day were imported that year? HINT [See Example 1.]