There are two LFSRs of different lengths: LFSR-17 and LFSR-25. LFSR-17 Initially contains a two byte seed, with a 1 injected into the fourth bit, for a total of 17 bits. LFSR-25 operates in the same way.
Of the 40-bit key, 2 bytes is seeded into the first LFSR and 3 bytes into the other. If the outputs of each LFSR were simply XORd to produce the keystream, how could we launch a known plaintext to retrieve the key?