A stopwatch manufacturing company has monthly fixed expenses of $48,000$\mathrm{}\mathrm{}\mathrm{}$ and a unit production cost of $8.$\mathrm{}$The stopwatches sell for $14 each. 

a.$.$ What is the cost function?

b.$.$ What is the revenue function?

c.$.$ What is the profit function?

d.$.$ Calculate the profit or loss corresponding to production levels of 4,000 and 6,000$\mathrm{<br>}$ units.