A company spends 2,000 to set up production, plus 15 per unit produced. Each unit sells for $35. How many units must be sold to break even?

Revenue equals cost at break-even. Revenue is $35x$, and total cost is $2000+15x$. Set them equal: $35x=2000+15x$, so $20x=2000$ and $x=100$ units, choice C. Check: revenue is $3,500, and cost is $2000+1500=3500$. Each unit contributes $20 toward the setup cost, because $35-15=20$. Choice B ($57$) divides the setup cost by the selling price, $\frac{2000}{35}$, ignoring the per-unit cost. Choice D ($133$) divides by $15 instead of $20. Choice A ($40$) is $\frac{2000}{50}$, which uses the sum of the costs and price incorrectly.