Seven thieves stole a chest of gold coins from a bank vault. When the thieves divided their loot into equal piles, (y + 1) coins were left over. Disagreement ensued and when they fought over who should get the extra coins, one of the thieves was killed. The remaining thieves divided the coins again into equal piles and 5 coins were left over. Again, the thieves fought over on who should get the extra coins and one of them was killed. Then the surviving thieves divided the coins into equal piles again. This time no coins were left over and the thieves were happy. (a) If y= a (mod 5) where a is the last digit of your student ID, find the least value of y. (1 mark) (b) Using the value of y obtained above, find the least number of coins the thieves could have stolen from the bank? (9 marks)