Write function bmi that calculates body mass index (bmi = weight / height2).
if bmi <= 18.5 return "Underweight"
if bmi <= 25.0 return "Normal"
if bmi <= 30.0 return "Overweight"
if bmi > 30 return "Obese"
def bmi(weight, height)
case weight/height**2
when 0..18.5
'Underweight'
when 18.6..25.0
'Normal'
when 25.0..30.0
'Overweight'
else
'Obese'
end
end