Problem.

The linear regression model of the cost C (in thousands of dollars) for the production of x toasters was found to be C(x) = 4x + 50

Question:

How many toasters must be sold for the cost to be less than $140000.00?

I understand we could solve for x if the cost is 140000. Subtract 1 from x and surely the cost would be less then 140000 but that doesnt make sense for linear regression . Could someone please help me understand how i would go abouts doing this?

Thanks alot.