We have a total of 26 letters and 10 algarisms.
After removing the letters I, B, Z and O, we will have 22 letters and 10 algarisms, therefore 32 options for each space.
a)
In order to find the number of licence plates available, we just need to multiply the number of possibilities for each space, so we have:
[tex]32\cdot32\cdot32\cdot32=1048576[/tex]b)
Since we have one more space, we just need to multiply the previous result by 32 again:
[tex]1048576\cdot32=33554432[/tex]c)
Dividing the values, we have:
[tex]\frac{33554432}{1048576}=32[/tex]