(7)\x05By using the digits 0,1,2,3,4 and 5 John arranges the number in ascending order as follow:\x050,1,2,3,4,5,10,11,12,13,14,15,20,21,22,23,24,25,30,31,….\x05(a)\x05How many of the 10-digit numbers have exactly three 4s?[4 marks]\x05(b)\x05What