Private O'Level.

Register for retaking Private O'level maths.
Total fees is $148.70.
Quite expensive uh.
But i'm still considering, cause i haven't pay, so still got time to think about it.
Last year when i took my O'level maths paper, i made a careless mistake and i think cause me to lose about 10marks. I know how to do that question you know, is just that i forgot to do one more step to get the correct answer. SO.... my 10marks gone...
So i'm thinking.. if is not because that careless mistake, maybe my grade will improve by 1? I don't know. This is just what i think lor.
Is it worth to pay $148 to just prove me wrong?? SHALL THINK ABOUT IT BEFORE I PAY THE FEES.