$5$ skilled workers can build a wall in $20$ days: $8$ semi-skilled workers can build a wall in $25$ days: $10$ unskilled workers can build a wall in $30$ days. If a team has $2$ skilled, $6$ semi-skilled and $5$ unskilled workers, how long will it take to build the wall?
- $20$ days
- $18$ days
- $16$ days
- $15$ days