Suppose that plaintext message units are trigraphs in the 32-letter

alphabet with A-Z corresponding to 0-25, blank=26, ?=27, !=28,

.=29, '=30, $=31. You receive the sequence of ciphertext message units

152472, 116116, 68546, 165420, 168261. The public key is the sequence

{24038, 29756, 34172, 34286, 38334, 1824, 18255, 19723, 143, 17146,

35366, 11204, 32395, 12958, 64791, and the secret key is b = 30966,

m = 47107. Decipher the message.