Klara has decided to file her tax return electronically. How will she benefit from e-filing?
A. She can expect a tax rebate for using a low-cost process and saving the IRS some paperwork.
B.
She can get free advice online from an IRS enrolled agent.
C.
If she's expecting a tax refund, e-filing can expedite the refund from the IRS.
D.
She can claim a special deduction and reduce the amount of taxes due.

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?

Afactory makes propeller drive shafts for ships. a quality assurance engineer at the factory needs to estimate the true mean length of the shafts. she randomly selects four drive shafts made at the factory, measures their lengths, and finds their sample mean to be 1000 mm. the lengths are known to follow a normal distribution whose standard deviation is 2 mm. calculate a 95% confidence interval for the true mean length of the shafts. input your answers for the margin of error, lower bound, and upper bound.

I’m stuck on this equation, anyone got the answer?