Can I risk this in the AM section?

Can I write 12.5M instead of 12,500,000? This is my habit of writing millions in 26.5M and thousands in 36k.

For questions with part i) and ii), the definition is written on i). Do I have to restate or refer my explanation on ii) from i)? On the mock, I put the calculations of both i) and ii) in the section under i) by accident. Since we are short on time, for ii), can I box the final answer and say see calculation in i)?

I think that that’s a common enough abbreviation.

A much better bet than, say, “+ve”.

I find myself habitually writing m = 1,000 and mm=1,000,000. Because it is easy enough to change, when I find myself writing I will change to the whole number, however once in a while I notice that I do not change. Any thoughts on m and mm if the calculations are correct?