Huanong Linux Experiment 6 Question 2

#! /bin/bash   
function help()  
{  
echo "Enter score:\n"  
}  
  
function menu()  
{  
  
while true  
do 
help 
read score  
if [ -z "$(echo $score | sed 's#[0-9]##g')" ]
then
if [ $score -ge 0 -a $score -lt 60  ]   
then   
echo "Failed"  
elif [ $score -ge 60 -a $score -lt 70 ]  
then   
echo "Passed"  
elif [ $score -ge 70 -a $score -lt 80 ]  
then  
echo "Medium"  
elif [ $score -ge 80 -a $score -lt 90 ]  
then  
echo "Good"  
elif [ $score -ge 90 -a $score -le 100 ]  
then  
echo "Excellent"  
else   
echo "error,please entry the score betwent 0 and 100"   
fi  
else   
echo "Please entry a number"  
fi 
done  
}  
  
echo "Welcome!"  
menu