well, for starters, is the 4 MH/s or do you live in a country that uses dots instead of commas and it's actually 4000
If it's 4 MH/s then your bill should be fine but you should probably check the specifications for the card your using and check how many watts it's using then you would just multiply that number by your hourly electricity charge (which is usually around €0.15) and by how long you are mining for.
If it's 4000 (which I highly doubt) then you must of bought an asic mining machine, congratulations! You are now making tonnes of money. The small amount of electricity that the asic uses is generally going to be a fraction of the money it generates