#### Answer

500 m; 700m

#### Work Step by Step

1. This is the ratio of the two shortest sides of the similar triangle. Reduced to make easier to solve equations
$\frac{4}{400}=\frac{1}{100}$
2. Then construct all three ratios to find unknown sides
$\frac{1}{100}=\frac{5}{a}=\frac{7}{b}$
3. Cross-multiplication --> Solutions :
a= 500
b= 700