exponential word problems

1.) Art Forgery. A painting attributed to Vermeer (1632 - 1675), a famous dutch painter, w/c should contain no more than 96.2% of its original carbon-14 contains 99.5% instead. About how old is the forgery? ( Carbon dating is a common technique of knowing or estimating the age of an object through its carbon content that undergoes a very slow decaying process)

2.) Polonium - 210. The half-life of polonium is 140 days, but your sample will not be useful to you after 95% of the radioactive nuclei present on the day the sample arrives has disintegrated. For about how many days after the sample arrives will you be able to use the polonium? ( 1st, research on the meaning and equation of half-life" before proceeding to solve this problem

3.) A beam of unknown temperature. An aluminum beam was brought into a machine shop where the temperature was held at 65 degrees F. After 10 minutes, the beam's temperature was 35 degrees F and after another 10 minutes it was 50 degrees Farenheight. Use Newton's Law of cooling to estimate the beam's initial temperature.

(The formula is T - Ts = ( To - Ts) e ^ -kt

where T is the temperature of the hot object at time t, Ts is the surrounding temperature that is assumed constant, To is the value of T at time zero and k is called the heat transfer coefficient, also a constant. The equation is also applicable to the case of a warming object.)

Very Sorry for being abusive!!