Find the velocity of a particle at \( t=4 \) given its position function. (position is in mi, time is in hr) \[ s(t)=19 t+7 \] \( v(4)=[?] \mathrm{mi} / \mathrm{hr} \)

To find the velocity of the particle at \( t=4 \), we first need to determine the velocity function, which is the derivative of the position function \( s(t) \). Given the position function: \[ s(t) = 19t + 7 \] We can differentiate it: \[ v(t) = s'(t) = \frac{d}{dt}(19t + 7) = 19 \] This means that the velocity is constant at 19 mi/hr for any time \( t \). Therefore, at \( t=4 \): \[ v(4) = 19 \text{ mi/hr} \]