m = 1
substituting the given values for D and v the equation can be expressed as
[tex]\frac{1}{4}[/tex] = [tex]\frac{m}{m+3}[/tex] (cross- multiply )
4m = m + 3 ( subtract m from both sides )
3m = 3 ( divide both sides by 3 )
m = 1 ← first value on list
