Assume that the rate of decay of a radioactive substance is proportional to the amount of the substance present. the half-life of a radioactive substance is the time it takes for one-half of the substance to disintegrate. carbon dating is often used to determine the age of a fossil. for example, a humanoid skull was found in a cave in south africa along with the remains of a campfire. archaeologists believe the age of the skull to be the same age as the campfire. it is determined that only 22% of the original amount of carbon-14 remains in the burnt wood of the campfire. complete parts (a) through (e) below. (a) estimate the age of the skull if the half-life of carbon-14 is about 5620 years the skull is about years old. round to the nearest whole number as needed.) (d) estimate the age of the skull if the half-life of carbon-14 is about 5610 years and 3% of the original amount of carbon-14 re e burnt the skull is about 28,380 years old round to the nearest whole number as needed.)