Let's substitute each letter of a given word by the value of its ordinal count in the ABC: A=>1, B==>2 .. Z==>26.
Evaluate the total for that word and call it f(k), k being the number of letters in the word.
Let MW(K) be a word for which f(k) is minimal.

Example: assuming the word CAB generates the lowest f(3) then MW(3) is CAB and its f(3)=6.

Question: What triplet of common English words will generate the lowest f(7)+f(9)+ f(11)?