please inform me about this

please solve my following queries.....

1.How can i prepare for oracle 10g OCA exam?

2.if cannot get first class in my academic degree ,and i have the certification of oca and ocp at that time wheather i can get good job or   not? Does the percentage affect or not?

3.If i have the oca certification and i do not have the ocp certification than is it enough or not?

4.What are the job avilable for oca and ocp certification holders?