3 or 4 a levels

Should I do 4 or 3 a levels?
We can't drop them anymore so I need to think carefully. I need to do maths and physics as i want to be an engineer. I don't know if I should take 3 maths physics and rm or 4 adding English lit. I don't know how hard I will find maths (I'm predicted a b for GCSE) and I need an A or A* at a level. I don't know if I should take 3 of 4 because I've been told that even if I take 3 my extra time will be filled with other lessons which makes me think i shoul do 4. Any ideas?

Why is it you cant drop a subject?.. I'm sure you can, even with the changing A-levels.

We have been told once you take it at as you must carry on with it until year 13. They have changed so all exams are done at the end of year 13 no more as, only full a levels. That's why I don't know if I should do 3 a levels and focus on the giving maths it's really hard and I need an A or A* or do 4.