Solve the programming task below in a Python markdown code block.
An NBA game runs 48 minutes (Four 12 minute quarters). Players do not typically play the full game, subbing in and out as necessary. Your job is to extrapolate a player's points per game if they played the full 48 minutes.

Write a function that takes two arguments, ppg (points per game) and mpg (minutes per game) and returns a straight extrapolation of ppg per 48 minutes rounded to the nearest tenth. Return 0 if 0.

Examples:
```python
nba_extrap(12, 20) # 28.8
nba_extrap(10, 10) # 48
nba_extrap(5, 17) # 14.1
nba_extrap(0, 0) # 0
```

Notes:
All inputs will be either be an integer or float.
Follow your dreams!
Also feel free to reuse/extend the following starter code:
```python
def nba_extrap(ppg, mpg):
```