Consider the following correspondence between letters/symbols and numbers: A=1, B=2, C=3, D=4, E=5, F=6, G=7, H=8, I=9, J=10, K=11, L=12, M=13, N=14, O=15, P=16, Q=17, R=18, S=19, T=20, U=21, V=22, W=23, X=24, Y=25, Z=26, a period is equal to 27, a comma is equal to 28, and # = 29.
Suppose that the secret message to be encoded is "THE PLOT THICKENS".
(a) Arrange the secret message into a numbers matrix M with 3 rows. Use the pound sign (#) to denote a space between letters.
(b) To encode the message, multiply matrix M on the left by matrix A where the encoding matrix A is defined as
3 1 2
2 1 -1
3 1 3