Vansh and Aman started a business with Rs. 20000 and Rs. 24000 respectively as their capital investment. Shubham joined them after M months and invested Rs. 36 000 and M months before the end of year Aman left the business. If at the end of the year share profit of Vansh, Aman and Shubham is in the ratio of 4 : 2 : 3, what is the value of M.