Help with producing a circuit that costs 17, then 9
the simplest I can manage using 2 input gates is 11

associative rule

X3'X0' + X2'X1'X0'  =  (X3' + X2'X1')X0'

Now apply de Morgan's theorem repeatedly.

M = (X3'+(X2+X1)') X0'

M = (X3(X2+X1))' X0'

M = ((X3(X2+X1))+X0)'

for a cost of 11

but the complement  M' = (X3(X2+X1))+X0)

for a cost of 9.