Advice needed - Limit selection

[liquidevil]

I started playing Poker online on July 04 and in 12 months I have been experimenting playing limits from $1/$2 to $5/$10. I recorded about 60k hands (about 80% on GBP1/2 limit) with a profit of 2.2BB/100 (only occasionally multitabling - and never more than 2 tables).

I thought what the hell I feel i am a winning player so i bought a new car (a good one) and I plan to have my poker game finance the car. So I need for the next 50 months, starting from August to earn $960 every month for the car.

This month I started experimenting with the micro limits and multitabling. I found out that i can easily play 4 tables at GBP 0.25/0.50 limit and so far in 10K hands my profit is about 9.5BB/100 (multitabling - 4 tables).

The question is .....

In order to earn the $960 per month that I need (and more if possible) should i

a) stick to GBP 0.25/0.50?

with 5hrs avg per day and 35 hands avg per hour the projection for every month is 5hrs * 4tables * 30 days = 600hrs

600 * 35 hands = 21.000 hands * 9BB/100 = 1890BB = GBP945 = about $1600 per month

or b) should i try to move in higher limits? (more ups and downs but my play will improve)