If Ram, Robert and Rahim started a firm by investing ₹50,000, ₹30,000 and ₹40,000 respectively for the same time period, then the ratio of the share of Rahim to that of Robert is _______, out of the profit of ₹18,000.

A

3 : 4

B

3 : 5

C

4 : 3

D

4 : 5