a , b and c invest in a partnership in the ratio : 7 / 24 / 36 / 5 . after 4 months , a increases his share 50 % . if the total profit at the end of one year is rs . 21600 , then what is b ' s share in the profit ?	Options:
A) 1000
B) 2000
C) 3000
D) 4000
E) 5000

Rationale: ratio of the initial investment = 7 / 2 : 4 / 3 : 6 / 5 = 105 : 40 : 36 therefore , let the initial investments of a , b and c be 105 x , 40 x and 36 x respectively a increases his share 50 % after 4 months . hence the ratio of their investments = ( 105 x × 4 ) + ( 105 x × 150 / 100 × 8 ) : 40 x × 12 : 36 x × 12 = 105 + ( 105 × 3 / 2 × 2 ) : 40 × 3 : 36 × 3 = 105 × 4 : 40 × 3 : 36 × 3 = 35 × 4 : 40 : 36 = 35 : 10 : 9 b ' s share = total profit × 10 / 54 = 21600 × 10 / 54 = 4000 answer is d .
Answer: D