Kala is mailing packages. each small package costs her $2.30 to send. each large package costs her 2.90. how much will it cost her to send 5 small packages and 7 small packages?

Witch represents the inverse of the function f(x)=1/4x-12

I'm confused on this could anyone me and show me what i need to do to solve it.

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.