To Help Kim Practice for the Special Olympics,Sally Runs Beside $\frac { t _ { K2m } } { 90 \mathrm {~s} }$

Multiple Choice

To help Kim practice for the Special Olympics,Sally runs beside him for half the required distance.She runs the remaining distance at her regular speed and arrives 90 seconds ahead of Kim.What is the ratio of Sally's regular speed to Kim's speed? Use t_Kim for Kim's total time.

A) $\frac { t _ { K2m } } { 90 \mathrm {~s} }$
B) $\frac { t _ { K2 m } } { t _ { K2 m} - 90 \mathrm {~s} }$
C) $\frac { t _ { K2 m } } { t _ { K2 m } - 180 \mathrm {~s} }$
D) $\frac { t _ { K 2m } } { 180 \mathrm {~s} }$
E) $\frac { t _ { K 2 m } - 90 \mathrm {~s} } { t _ { K 2m } - 180 \mathrm {~s} }$