John is going to take two exams for his degree course next week. The first one is more difficult and he feels that the probability he will pass this exam is 3∕4, while he is more confident about the second one giving a success probability to himself of 9∕10. The probability that John passes at least one of these two exams is

(a) 4∕5

(b) 39∕40

(c) 19∕20

(d) 1

(e) none of the above