Problem 4. On a board, eight numbers equal to 0 are written, one after another. We call an operation the modification of four of the eight numbers as follows: two numbers increase by 3, one number increases by 2, and the fourth number increases by 1.

a) What is the minimum number of operations we need to perform to obtain eight consecutive natural numbers on the board.

b) Is it possible that, after a number of operations, all the numbers written on the board are equal to 2015?

c) Is it possible that, after a sequence of operations, the product of the numbers on the board is 2145?