The number of four-digit numbers strictly greater than 4321 that can be formed using the digits 0,1,2,3,4,5 (repetition of digits is allowed) is :

(1) The number of four-digit numbers Starting

with 5 is equal to $6^{3}=216$

(2) Starting with 44 and 55 is equal to

$36 \times 2=72$

(3) Starting with 433,434 and 435 is equal to

$6 \times 3=18$

(3) Remaining numbers are

$4322,4323,4324,4325$ is equal to 4

so total numbers are

216 + 72 + 18 + 4 = 310