The text below was encrypted with a substitution cipher. Only the letters (both
upper-case and lower-case) were substituted, leaving punctuation and spaces alone.
Can any on help me to figure out what the original message was using maple procedures.
“wA’r aBeD WUeK AP XNaB NM U rALKNP USUeAJBMA NM zUM
nPrB ZNAW U JUM ZWP’r XBUeMNMO AP SXUD AWB aNPXNM.”
yWUA’r ZWUArWBAPXK AWB SPXNCB ZWBMrWBWUMKBK AWBJ
AWB BJSAD eBaPXaBe.
lNCWUeK heULANOUM, “yWB zCUeXUAAN yNXA”

I have no clue...

how to write a procedure that counts ferquency of used letters in a string of a text for ex in this txt: fregs("I have the best dog.");