Need some more explanation of problem

#1

Can you please explain ,how minimum time is 12?

#2

Can you please look at my code and tell me where I am wrong https://ide.codingblocks.com/s/114640

#3

chef with rank 4 will make 4,8 = 2 parathas in 12 minutes,
chef with rank 3 makes 3,6 = 2 parthas in 9 minues
chef with rank 2 makes 2,4,6 = 3 parthas in 12 minues
chef with rank 1 makes 1,2,3,4 = 4 parthas in 10 minues
therefore in less than 12 minutes 10 arathas are made

#4
#5

I understood the distribution.I used same approach to solve problem but I am getting error while submission.
Can you please look my code and tell me where I am wrong