OK. M means molarity, that's moles per liter, whereas m means molality, which is moles per kg of solution. You simply have to get it right.
Trivia: Italian doesn't have the letter 'k', all metric weights are listed as 'cilo' in supermarkets. However, every scientist in Italy uses this mysterious, unknown assortment of lines, that everyone else calls 'k', when doing work.
Ok, back to work: Neither M or m means moles, which may occasionally be abbreviated mol. And you will have to be able to balance a simple equation like this one, they have put it on the test just to trick you -- the answer would be different for 0.3 M HCl, as an example.