The following accompanying table shows the relationship between the speed of a computer's CPU and its benefits and costs. Assume that all other features of the computer are the same $($that is$,$ CPU speed is the only source of variation$),$ and only the CPU speeds listed below are available for purchase.

CPU GHz

Total Benefit

Marginal Benefit

Total Cost

Marginal Costs

$2\mathrm{.}0$

$$1,000$

$$900$

$2\mathrm{.}5$

$$1,400$

$$100$

$3\mathrm{.}0$

$$300$

$$1,200$

$3\mathrm{.}5$

$$1,900$

$$1,500$

$4\mathrm{.}0$

$$2,000$

$$400$

Application of the Cost$-$Benefit Principle would lead one to purchase a $\_\_\_\_\_\_$ computer.

Group of answer choices

$2\mathrm{.}5$ GHz

$4\mathrm{.}0$ GHz

$3\mathrm{.}0$ GHz

$2\mathrm{.}0$ GHz