*i need with learning cross property* (i was sick and missed a lot of school) the questions i need on are: 14/21=b/9 ; 10/p=6/9 ; 55/4=h/6

Suppose you are choosing a 6-digit personal access code. this code is made up of 4 digits chosen from 1 to 9, followed by 2 letters chosen from a to z. any of these digits or letters can be repeated. find the total number of personal access codes that can be formed. 492,804 341,172 39,917,124 4,435,236