Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Problem: ( ( - 1.9 ) ( 0.6 ) – ( 2.6 ) ( 1.2 ) ) / 2.0 = ?
Options: a. - 0.71, b. - 2.13, c. 1.07, d. 1.71, e. 2.71
b

Problem: in 10 years, a will be twice as old as b was 10 years ago. if a is now 5 years older than b the present age of b is
Options: a. 37, b. 38, c. 39, d. 35, e. 41
d

Problem: jo ' s collection contains us, indian and british stamps. if the ratio of us to indian stamps is 5 to 2 and the ratio of indian to british stamps is 5 to 1, what is the ratio of us to british stamps ?
Options: a. 10: 5, b. 15: 2, c. 20: 2, d. 25: 2, e. none of these

d