$(1$ point$)$ Encrypt the message $"$ HALT $"$ by translating the letters into numbers

$($via $A=0,B=1,C=2,D=3,E=4,F=5,G=6,H=7,I=8,$

$J=9,K=10,L=11,M=12,N=13,O=14,P=15,Q=16,R=17,$

$S=18,T=19,U=20,V=21,W=22,x=23,Y=24,Z=25)$

and then applying the encryption function given, and then translating the numbers back into letters.

$($a$)f(p)=(p+5)mod26$

$($b$)f(p)=(p+9)mod26$

$($c$)f(p)=(p+4)mod26$