7. rubí por el dia de su cumpleaños recibe s/. 200 de
propina, gasta el 30 % en un polo y luego gasta el
50 % de lo que le queda en un pantalón, ¿cuánto
dinero aún le queda?
a) s/. 70
d) 20
b) 60
e) 120 c) 40
ayudame es para hoy día por favor

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.