HELP HELP HELP !!! PLEASE

FOR JUNE 2010 PART (a) this is how I calculated the closing balance for (i) & (ii):

(i) 1st period : -500,000 + (8,000,000 x 0.1) + (4,000,000 x 0.6) – (2,000,000 x 0.3) = $2,100,000

(ii) 2nd period: 2,100,000 + (7,000,000 x .3) + (3,000,000 x .5) – (9,000,000 x .2) = $3,900,000

but I can’t proceed further to calculate (iii) the probability of negative cash balance at the end of period 2 … (iv) the probability of exceeding the overdraft limit at the end of period 2

please can anyone explain me how to calculate (iii) & (iv) using the same approach that i’ve used… I want to make it as as simple as possible

and I also want to know what is capital gains??