Answer
$2.0\hat{k}$
Work Step by Step
Use
$\vec{a}\times\vec{b}=(a_{y}b_{z}-b_{y}a_{z})\hat{i}+(a_{z}b_{x}-b_{z}a_{x})\hat{j}+(a_{x}b_{y}-b_{x}a_{y})\hat{k}\qquad$ (3-27)
$\vec{a}=3.0\hat{i}+5.0\hat{j}+0\hat{k}$
$\vec{b}=2.0\hat{i}+4.0\hat{j}+0\hat{k}$
$\vec{a}\times\vec{b}=(0)\hat{i}+(0)\hat{j}+(3.0\cdot 4.0-2.0\cdot 5.0)\hat{k}=2.0\hat{k}$
