Chico can produce the following combinations of X and Y: $10$X and $10$Y$,5$X and $15$Y$,$ and $0$X and $20$Y$.$ The opportunity cost of one unit of X for Chico is

Group of answer choices

$1$ unit of Y$.$

$2$ units of Y$.$

$1/2$ unit of Y$.$

$1/4$ unit of Y$.$

not shown