For problem $7\mathrm{.}7$: What is the value of Ay and By$?$

$10\mathrm{.}5k$ and $9\mathrm{.}5k$

$6k$ and $7\mathrm{.}5k$

$11k$ and $12k$

$12\mathrm{.}5k$ and $6\mathrm{.}5k$