You are planning a study to determine if mean height in a population has
changed. The populations mean height in 1920 was 64 inches with a standard
deviation of 4 inches. The study needs a big enough sample to detect a change
of 1% with a power 0.8 and a significance of 0.05. How big should the sample
be?

A 307
B 70
C 69.09
D 306.25

Aspacecraft can attain a stable orbit 300 kilometers above earth if it reaches a velocity of 7.7 kilometers per second. the formula for a rocket's maximum velocity v in kilometers per second is vequalsminus0.0098tplusc ln upper r, where t is the firing time in seconds, c is the velocity of the exhaust in kilometers per second, and r is the ratio of the mass of the rocket filled with fuel to the mass of the rocket without fuel. find the velocity of a spacecraft whose booster rocket has a mass ratio of 20, an exhaust velocity of 2.1 km/s, and a firing time of 15 s. can the spacecraft achieve a stable orbit 300 km above earth?