The life span at birth of humans has a mean of 89.87 years and a standard deviation of 16.63 years. calculate the upper and lower bounds of an interval containing 95% of the sample mean life spans at birth based on samples of 105 people. give your answers to 2 decimal places.

Suppose there is a simple index of three stocks, stock abc, stock xyz, and stock qrs. stock abc opens on day 1 with 4000 shares at $3.15 per share. stock xyz opens on day 1 with 5000 shares at $4.30 per share. stock qrs opens on day 1 with 6000 shares at $4.60 per share. the price of stock abc on day 8 begins at $3.50. the price of stock xyz on day 8 begins at $3.90. stock qrs opens on day 8 with a price of $4.50 per share. assume that each stock has the same number of shares that it opened with on day 1. what is the rate of change of this simple index over 1 week?

Two streets intersect at a 30- degree angle. at the intersection, the are four crosswalks formed that are the same length. what type of quadrilateral is formed by the crosswalks?

Given sin28.4=.4756, cos28.4=.8796, and tan28.4=.5407 find the cos of 61.6