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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def systemInformationType4(ChannelDescription_presence=0, MobileAllocation_presence=0):
 """SYSTEM INFORMATION TYPE 4 Section 9.1.36"""

    a = L2PseudoLength()
    b = TpPd(pd=0x6)
    c = MessageType(mesType=0x1C)  # 000111100
    d = LocalAreaId()
    e = CellSelectionParameters()
    f = RachControlParameters()
    packet = a / b / c / d / e / f
    if ChannelDescription_presence is 1:
        g = ChannelDescriptionHdr(ieiCD=0x64, eightBitCD=0x0)
        packet = packet / g
    if MobileAllocation_presence is 1:
        h = MobileAllocationHdr(ieiMA=0x72, eightBitMA=0x0)
        packet = packet / h
    i = Si4RestOctets()
    packet = packet / i
    return packet