A boat goes downstream and covers the distance between two ports in 4 hours while it covers the same distance upstream in 5 hours. If the speed of the stream is \[2\text{ }kmph,\] what is the speed of the boat in still water?

• A.  \[15\text{ }kmph\]                        
• B.                         \[20\text{ }kmph\]                        
• C.                         \[24\text{ }kmph\]                        
• D.                         \[\text{18 }kmph\]