total = 10\times50\times100 = 50000
i got the y and z fungibility(when y is 1 digit and z is two digit, which accounts for 3240 cases, when 1<=z<=9 and 11<=y<=49 and y is not equal to 20, 30, 40), which accounts to = 36\times9\times10 = 3240
so the answer should be 50000-3240= 46760, but the answer is 46320.