A mobile phone must pass two independent hardware tests H1 and H2 followed by a software test S. Given P(H1)=0.9, P(H2)=0.95, and P(S∣H1∩H2)=0.8, determine the probability that a phone passes all three tests.
a) 0.855
b) 0.760
c) 0.684
d) 0.796