Swapping Knights and Bishops

Place a white knight and a white bishop at locations 1 and 3 of the 4x5 chessboard shown. Place a black knight and a black bishop at locations 17 and 19.
 4x5 board
|WK| 5| 9|13|BK|
| 2| 6|10|14|18|
|WB| 7|11|15|BB|
| 4| 8|12|16|20|
Starting from this position,
  1. Swap the positions of the white knight and white bishop.
  2. Swap the colors (swap the positions of the two knights and the two bishops.)
At no time may any piece be under attack by a piece of the opposite color. Moves do not need to alternate in color.
Source: Original. Similar to Puzzle of July 20, 1998. I'd be interested if this could be made more difficult, perhaps by placing four pieces on each side.
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