Answer:
A. 10,000 combinations
B. 5,040 combinations
Step-by-step explanation:
A. four-digit code from 0-9 without restriction
1st digit - 10 options
2nd digit - 10 options
3rd digit - 10 options
4th digit - 10 options
Number of possible options = 10 * 10 * 10 * 10 = 10^4 = 10,000 combinations
b. No repetition of digits
1st digit = 10 options
2nd digit = 9 options
3rd digit = 8 options
4th digit = 7 options
Number of possible choices = 10 * 9 * 8 * 7 = 5,040 combinations
