Answer:
b. 63 minutes
Step-by-step explanation:
Given;
number of times the hash function is applied = 12
time taken to brute force one application, = 21 minutes
Apply proportion, bearing in mind that 4 available resources should take less time;
1 available resource ------- 21 minutes
4 available resources ------ x
Thus, x = 21 minutes / 4
When applied 12 times, the time should be [tex]\frac{21 \ minutes}{4} \ \times \ 12 \ = 63 \ minutes \\\\[/tex]
Therefore, the correct option is B, 63 minutes
