$1|$ def letter$\_$grade$($score:float$)->$ str:

$2|$ if score $>=90\mathrm{.}0$:

$3|$ grade $=\text{'}$A$\text{'}$

$4|$ elif score $>=80\mathrm{.}0$:

$5|$ grade $=\text{'}$B$\text{'}$

$6|$ elif score $>=70\mathrm{.}0$:

$7|$ grade $=\text{'}$C$\text{'}$

$8|$ elif score $>=60\mathrm{.}0$:

$9|$ grade $=\text{'}$D$\text{'}$

$10|$ else:

$11|$ grade $=\text{'}$F$\text{'}$

$12|$ return grade

$14|$ grade $=78\mathrm{.}50$

$15|$ answer $=$ letter$\_$grade$($grade$)$