Rs 4000 is divided into two parts such that one part is put out at 3% and the other at 5%. If the annual interest earned from both the investments be Rs 144, find the first part. Choose the correct choice
A) rs 4000  B) rs 2800  C) rs 3800  D) rs 3500  E) rs 3100

Rationale: "explanation : average rate = ( 144 / 4000 ) * 100 = 3.6 ratio = 14 : 6 = 7 : 3 so , first part = ( 7 / 10 ) * 4000 = rs 2800 . answer : b"
Answer: B