mother and dauther maintanense

My mother got maintanense in 1999. Amount 500 rupees for each one.total 3.when his salary was 3500..we are two sister (24yrs),me(boy 26yrs).now my father salary was 62000..my sister unmarried..now my mother want to file a maintanense case...my question is my sister is eligible to get maintanense or not ?? Plzz answer me... How much they get ? Thanku sir