Vat querry

Hey, I hv query regardin VAT, Plss giv ur suggestions :

one person is havin two division, one is furniture and other is food. they hv taken single vat registration no. n VAT @ 12.5 % is charged on selling furniture n food items. now, the food div wants to go for composition scheme as the rate of vat will be lesser. 

my query is whether they can do it wid same VAT no. n if yes wht is d procedure? n how it can b reflected in VAT return?