Sarat, Chandra and Mayank completed a job in 10 days in the following manner-they worked together for 3 days in which they completed 37 percent of the total work.But due to unavoidable circumstances, sharat quits the job at this point and rest of the two worked together to complete the job.if the work done by chandra in 4 days is equal to the work done by mayank in 5 days, then what is the time required by the fastest worker to complete the work alone?approach please

1) 20 days
2) 25 days
3) 30 days
4) none of these