Solve
-A Boat Moves 5 Kilometers Upstream in the Same $9 \mathrm {~km} / \mathrm { hr }$

Solve.
-A boat moves 5 kilometers upstream in the same amount of time it moves 20 kilometers downstream. If the rate of the current is 9 kilometers per hour, find the rate of the boat in still water.

A) $9 \mathrm {~km} / \mathrm { hr }$
B) $6 \frac { 2 } { 3 } \mathrm {~km} / \mathrm { hr }$
C) $15 \mathrm {~km} / \mathrm { hr }$
D) $3 \mathrm {~km} / \mathrm { hr }$