Answer
$H(t)=1.75t^{2}+65t+700 \quad $(billion dollars)
Work Step by Step
$H(t)=\displaystyle \int(3.5t+65)dt$
$=3.5\displaystyle \cdot\frac{t^{2}}{2}+65t+C$
$=1.75t^{2}+65t+C$
To find C, use the given information: $H(0)=700$
$700=0+0+C$
$C=700$
Thus,
$H(t)=1.75t^{2}+65t+700 \quad $(billion dollars)
