Answer the questions on the basis of the information given below.
Purana and Naya are two brands of kitchen mixer-grinders available in the local market. Purana is an old brand that was introduced in $1990$, while Naya was introduced in $1997$. For both these brands, $20\%$ of the mixer-grinders bought in a particular year are disposed off as junk exactly two years later. It is known that $10$ Purana mixer-grinders were disposed off in $1997$. The following figures show the number of Purana and Naya mixer-grinders in operation from $1995$ to $2000$, as at the end of the year.
How many Purana mixer-grinders were disposed off in $2000$?
- $0$
- $5$
- $6$
- Cannot be determined from the data