The current exchange rate is $17\mathrm{.}31$ MXN per $1$ USD. A Toyota Corolla costs $$20,000$ in San Antonio, Texas. A similar Toyota Corolla costs MXN $400,000$ in Monterrey, Mexico.

What is the implicit exchange rate based on the price of the Corollas in San Antonio and in Mexico?

$17\mathrm{.}31$ MXN per $1$ USD

$17\mathrm{.}31$ USD per $1$ MXN

$20$ MXN per $1$ USD

$0\mathrm{.}058$ USD per MXN