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: for 2 consecutive yrs, my incomes are in the ratio of 4: 7 and expenses in the ratio of 3: 5. if my income in the 2 nd yr is rs. 42000 & my expenses in the first yr in rs. 23000, my total savings for the two - year is
Options: a. s. 8000, b. s. 9000, c. s. 9900, d. s. 9990, e. s. 10000
a

Problem: a certain protective additive increases from 50 days to 60 days the time between required maintenance checks on an industrial vehicle. by what percent is the time between maintenance checks increased by using the additive ?
Options: a. 25 %, b. 33 1 / 3 %, c. 50 %, d. 66 2 / 3 %, e. 20 %
e

Problem: last year a worker saved 6 % of her annual salary. this year, she made 20 % more money than last year and she saved 5 % of her salary. the amount she saved this year was what percent of the amount she saved last year ?
Options: a. 90 %, b. 100 %, c. 110 %, d. 120 %, e. 130 %

b