A 7% tax on $400 means an extra 7% of $400.<br><br>
&bull; Tax = 7% of $400 = \(\frac{7}{100} \times 400\) = 7 × 4 = $28<br>
&bull; Total = $400 + $28 = $428<br>
&bull; This matches option D: $428.<br><br>
Final Answer: D: $428