Laplace Transforms · Easy problem

Using $\mathcal{L}\{t^{a}\} = \dfrac{\Gamma(a+1)}{s^{a+1}}$ and $\Gamma\!\left(\tfrac32\right) = \dfrac{\sqrt{\pi}}{2}$, find $\mathcal{L}\{\sqrt{t}\}$ evaluated at $s = 4$.