Add Comments to the specifi lines i na file

UNIX for Advanced & Expert Users
1

I have a requirement like below.I need to Comment some lines in a file.

File contains following information.

{
attribute1
attribute2
atrribute3
attribute4
attribute5
attribute6
attribute7
}

I have a requirement like some times i need to comment lines 3 to before '}' and some times from 5 to before '}'

Out Put for scenario1
{
attribute1
attribute2
//atrribute3
//attribute4
//attribute5
//attribute6
//attribute7
}

Out Put for schenario2
{
attribute1
attribute2
atrribute3
attribute4
//attribute5
//attribute6
//attribute7
}

Can any one please help me how can i acheive this.

Thanks

2 
sed -e '/attribute3/,/attribute7/ s/.*/\/\/&/ ' file