Suppose in a computer network, 36% of computers have antivirus software, 30% of computers have a firewall, and 22% of the computers with antivirus software also have a firewall. Now, a computer is randomly chosen and found to have a firewall. What is the probability that it also has antivirus software?
a. 0.22
b. 0.27
c. 0.30
d. 0.36