$1-$Mobile provides cellular phone and Interinet services with a plan that provides up to $1,000$ minutes of airtime usage for a flat rad of $$99\mathrm{.}99$ per month plus a charge for any minutes used over this amount at the rate of $$0\mathrm{.}10$ per minute in excess of the minimum $1,000$ airtime minutes. Which of the following describes the cost of the j Mobile senice$?$

sem$/$fred cost$.$

variable cent, only.

mined cost.

freed cost, only.