what is the answer for this an arithmetical progression has positive terms.the ratio of the difference of the 4th and 8th term to the 15th t

what is the answer for this an arithmetical progression has positive terms.the ratio of the difference of the 4th and 8th term to the 15th term is 4/15 and the square of the difference of the 4th and the 1st term is 225 which term of the series is 2015