$A$ river is flowing at a speed of $5\, km/h$ in a particular direction. $A$ man,who can swim at a speed of $20\, km/h$ in still water,starts swimming along the direction of flow of the river from point $A$ and reaches another point $B$ which is at a distance of $30\, km$ from the starting point $A$. On reaching point $B$,the man turns back and starts swimming against the direction of flow of the river and stops after reaching point $A$. The total time taken by the man to complete his journey is:

• A
  $2\, h\, 30\, min$
• B
  $3\, h\, 12\, min$
• C
  $3\, h\, 30\, min$
• D
  $3\, h\, 45\, min$