(b) Given, $a = \alpha t + \beta$
$\frac{dv}{dt} = \ \alpha t + \beta$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \int_{0}^{t}{dv} = \int_{0}^{t}{\alpha t}dt + \int_{0}^{t}\beta dt$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ v = \frac{\alpha t^{2}}{2} + \beta t$