<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def trk50(msg):
 """True track angle, BDS 5,0 message Args: msg (String):
 28 bytes hexadecimal message (BDS50) string Returns: float: angle in degrees to true north (from 0 to 360) """

    d = hex2bin(data(msg))

    if d[11] == '0':
        return None

    sign = int(d[12])   # 1 -> west
    value = bin2int(d[13:23])

    if sign:
        value = value - 1024

    trk = value * 90.0 / 512.0

    # convert from [-180, 180] to [0, 360]
    if trk < 0:
        trk = 360 + trk

    return round(trk, 3)