Epf calculation

Dear All,

I have two queries relating to EPF calulation. My questions are given below:-

1) Suppose working days in a co. in a particular month (say May) is 24days. An employee took 6 leaves (leaves without pay) and his basic salary is Rs. 13,000/-. My question is EPF for the m/o May is calculated on what amount i.e on 13,000 or on proportionate amount i.e 13000/24*18?

2) Suppose company pay arrears of Rs. 2000 in the m/o June. And an employee basic salary is Rs. 13,000. So, EPF for the m/o June is calculated on what amount- on 13,000 or on 15000?

I need clear explanation. Please guide me.

Regards 

Khushboo Goyal