An important numerical calculation on a spacecraft is carried out independently by three computers. If all arrive at the same answer it is deemed correct. If one disagrees it is overruled. If there is no agreement then a fourth computer does the calculation and, if its answer agrees with any of the others, it is deemed correct. The probability of an individual computer getting the answer right is 99%. Use a tree diagram to find:

(a) The probability that the first three computers get the right answer; 

(b) The probability of getting the right answer;

(c) The probability of getting no answer;

(d) The probability of getting the wrong answer.