A business gives its employees $2$ for every unit of X they assemble and $3.20$ for each unit of Y they assemble. Each month, output is $1800$ units of X and $1000$ units of Y. The factory supervisor earns $1000$ per month. How much is the direct labour cost per month?
- A$6800$
- B$7760$
- C$7800$
- D$8760$